// RB tree implementation -*- C++ -*-
	
	// Copyright (C) 2001-2017 Free Software Foundation, Inc.
	//
	// This file is part of the GNU ISO C++ Library.  This library is free
	// software; you can redistribute it and/or modify it under the
	// terms of the GNU General Public License as published by the
	// Free Software Foundation; either version 3, or (at your option)
	// any later version.
	
	// This library is distributed in the hope that it will be useful,
	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	// GNU General Public License for more details.
	
	// Under Section 7 of GPL version 3, you are granted additional
	// permissions described in the GCC Runtime Library Exception, version
	// 3.1, as published by the Free Software Foundation.
	
	// You should have received a copy of the GNU General Public License and
	// a copy of the GCC Runtime Library Exception along with this program;
	// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
	// <http://www.gnu.org/licenses/>.
	
	/*
	 *
	 * Copyright (c) 1996,1997
	 * Silicon Graphics Computer Systems, Inc.
	 *
	 * Permission to use, copy, modify, distribute and sell this software
	 * and its documentation for any purpose is hereby granted without fee,
	 * provided that the above copyright notice appear in all copies and
	 * that both that copyright notice and this permission notice appear
	 * in supporting documentation.  Silicon Graphics makes no
	 * representations about the suitability of this software for any
	 * purpose.  It is provided "as is" without express or implied warranty.
	 *
	 *
	 * Copyright (c) 1994
	 * Hewlett-Packard Company
	 *
	 * Permission to use, copy, modify, distribute and sell this software
	 * and its documentation for any purpose is hereby granted without fee,
	 * provided that the above copyright notice appear in all copies and
	 * that both that copyright notice and this permission notice appear
	 * in supporting documentation.  Hewlett-Packard Company makes no
	 * representations about the suitability of this software for any
	 * purpose.  It is provided "as is" without express or implied warranty.
	 *
	 *
	 */
	
	/** @file bits/stl_tree.h
	 *  This is an internal header file, included by other library headers.
	 *  Do not attempt to use it directly. @headername{map,set}
	 */
	
	#ifndef _STL_TREE_H
	#define _STL_TREE_H 1
	
	#pragma GCC system_header
	
	#include <bits/stl_algobase.h>
	#include <bits/allocator.h>
	#include <bits/stl_function.h>
	#include <bits/cpp_type_traits.h>
	#include <ext/alloc_traits.h>
	#if __cplusplus >= 201103L
	# include <ext/aligned_buffer.h>
	#endif
	#if __cplusplus > 201402L
	# include <bits/node_handle.h>
	#endif
	
	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	
	#if __cplusplus > 201103L
	# define __cpp_lib_generic_associative_lookup 201304
	#endif
	
	  // Red-black tree class, designed for use in implementing STL
	  // associative containers (set, multiset, map, and multimap). The
	  // insertion and deletion algorithms are based on those in Cormen,
	  // Leiserson, and Rivest, Introduction to Algorithms (MIT Press,
	  // 1990), except that
	  //
	  // (1) the header cell is maintained with links not only to the root
	  // but also to the leftmost node of the tree, to enable constant
	  // time begin(), and to the rightmost node of the tree, to enable
	  // linear time performance when used with the generic set algorithms
	  // (set_union, etc.)
	  // 
	  // (2) when a node being deleted has two children its successor node
	  // is relinked into its place, rather than copied, so that the only
	  // iterators invalidated are those referring to the deleted node.
	
	  enum _Rb_tree_color { _S_red = false, _S_black = true };
	
	  struct _Rb_tree_node_base
	  {
	    typedef _Rb_tree_node_base* _Base_ptr;
	    typedef const _Rb_tree_node_base* _Const_Base_ptr;
	
	    _Rb_tree_color	_M_color;
	    _Base_ptr		_M_parent;
	    _Base_ptr		_M_left;
	    _Base_ptr		_M_right;
	
	    static _Base_ptr
	    _S_minimum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	    {
	      while (__x->_M_left != 0) __x = __x->_M_left;
	      return __x;
	    }
	
	    static _Const_Base_ptr
	    _S_minimum(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	    {
	      while (__x->_M_left != 0) __x = __x->_M_left;
	      return __x;
	    }
	
	    static _Base_ptr
	    _S_maximum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	    {
	      while (__x->_M_right != 0) __x = __x->_M_right;
	      return __x;
	    }
	
	    static _Const_Base_ptr
	    _S_maximum(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	    {
	      while (__x->_M_right != 0) __x = __x->_M_right;
	      return __x;
	    }
	  };
	
	  // Helper type offering value initialization guarantee on the compare functor.
	  template<typename _Key_compare>
	    struct _Rb_tree_key_compare
	    {
	      _Key_compare		_M_key_compare;
	
	      _Rb_tree_key_compare()
	      _GLIBCXX_NOEXCEPT_IF(
		is_nothrow_default_constructible<_Key_compare>::value)
	      : _M_key_compare()
	      { }
	
	      _Rb_tree_key_compare(const _Key_compare& __comp)
	      : _M_key_compare(__comp)
	      { }
	
	#if __cplusplus >= 201103L
	      // Copy constructor added for consistency with C++98 mode.
	      _Rb_tree_key_compare(const _Rb_tree_key_compare&) = default;
	
	      _Rb_tree_key_compare(_Rb_tree_key_compare&& __x)
		noexcept(is_nothrow_copy_constructible<_Key_compare>::value)
	      : _M_key_compare(__x._M_key_compare)
	      { }
	#endif
	    };
	
	  // Helper type to manage default initialization of node count and header.
	  struct _Rb_tree_header
	  {
	    _Rb_tree_node_base	_M_header;
	    size_t		_M_node_count; // Keeps track of size of tree.
	
	    _Rb_tree_header() _GLIBCXX_NOEXCEPT
	    {
	      _M_header._M_color = _S_red;
	      _M_reset();
	    }
	
	#if __cplusplus >= 201103L
	    _Rb_tree_header(_Rb_tree_header&& __x) noexcept
	    {
	      if (__x._M_header._M_parent != nullptr)
		_M_move_data(__x);
	      else
		{
		  _M_header._M_color = _S_red;
		  _M_reset();
		}
	    }
	#endif
	
	    void
	    _M_move_data(_Rb_tree_header& __from)
	    {
	      _M_header._M_color = __from._M_header._M_color;
	      _M_header._M_parent = __from._M_header._M_parent;
	      _M_header._M_left = __from._M_header._M_left;
	      _M_header._M_right = __from._M_header._M_right;
	      _M_header._M_parent->_M_parent = &_M_header;
	      _M_node_count = __from._M_node_count;
	
	      __from._M_reset();
	    }
	
	    void
	    _M_reset()
	    {
	      _M_header._M_parent = 0;
	      _M_header._M_left = &_M_header;
	      _M_header._M_right = &_M_header;
	      _M_node_count = 0;
	    }
	  };
	
	  template<typename _Val>
	    struct _Rb_tree_node : public _Rb_tree_node_base
	    {
	      typedef _Rb_tree_node<_Val>* _Link_type;
	
	#if __cplusplus < 201103L
	      _Val _M_value_field;
	
	      _Val*
	      _M_valptr()
	      { return std::__addressof(_M_value_field); }
	
	      const _Val*
	      _M_valptr() const
	      { return std::__addressof(_M_value_field); }
	#else
	      __gnu_cxx::__aligned_membuf<_Val> _M_storage;
	
	      _Val*
	      _M_valptr()
	      { return _M_storage._M_ptr(); }
	
	      const _Val*
	      _M_valptr() const
	      { return _M_storage._M_ptr(); }
	#endif
	    };
	
	  _GLIBCXX_PURE _Rb_tree_node_base*
	  _Rb_tree_increment(_Rb_tree_node_base* __x) throw ();
	
	  _GLIBCXX_PURE const _Rb_tree_node_base*
	  _Rb_tree_increment(const _Rb_tree_node_base* __x) throw ();
	
	  _GLIBCXX_PURE _Rb_tree_node_base*
	  _Rb_tree_decrement(_Rb_tree_node_base* __x) throw ();
	
	  _GLIBCXX_PURE const _Rb_tree_node_base*
	  _Rb_tree_decrement(const _Rb_tree_node_base* __x) throw ();
	
	  template<typename _Tp>
	    struct _Rb_tree_iterator
	    {
	      typedef _Tp  value_type;
	      typedef _Tp& reference;
	      typedef _Tp* pointer;
	
	      typedef bidirectional_iterator_tag iterator_category;
	      typedef ptrdiff_t                  difference_type;
	
	      typedef _Rb_tree_iterator<_Tp>        _Self;
	      typedef _Rb_tree_node_base::_Base_ptr _Base_ptr;
	      typedef _Rb_tree_node<_Tp>*           _Link_type;
	
	      _Rb_tree_iterator() _GLIBCXX_NOEXCEPT
	      : _M_node() { }
	
	      explicit
	      _Rb_tree_iterator(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      : _M_node(__x) { }
	
	      reference
	      operator*() const _GLIBCXX_NOEXCEPT
	      { return *static_cast<_Link_type>(_M_node)->_M_valptr(); }
	
	      pointer
	      operator->() const _GLIBCXX_NOEXCEPT
	      { return static_cast<_Link_type> (_M_node)->_M_valptr(); }
	
	      _Self&
	      operator++() _GLIBCXX_NOEXCEPT
	      {
		_M_node = _Rb_tree_increment(_M_node);
		return *this;
	      }
	
	      _Self
	      operator++(int) _GLIBCXX_NOEXCEPT
	      {
		_Self __tmp = *this;
		_M_node = _Rb_tree_increment(_M_node);
		return __tmp;
	      }
	
	      _Self&
	      operator--() _GLIBCXX_NOEXCEPT
	      {
		_M_node = _Rb_tree_decrement(_M_node);
		return *this;
	      }
	
	      _Self
	      operator--(int) _GLIBCXX_NOEXCEPT
	      {
		_Self __tmp = *this;
		_M_node = _Rb_tree_decrement(_M_node);
		return __tmp;
	      }
	
	      bool
	      operator==(const _Self& __x) const _GLIBCXX_NOEXCEPT
	      { return _M_node == __x._M_node; }
	
	      bool
	      operator!=(const _Self& __x) const _GLIBCXX_NOEXCEPT
	      { return _M_node != __x._M_node; }
	
	      _Base_ptr _M_node;
	  };
	
	  template<typename _Tp>
	    struct _Rb_tree_const_iterator
	    {
	      typedef _Tp        value_type;
	      typedef const _Tp& reference;
	      typedef const _Tp* pointer;
	
	      typedef _Rb_tree_iterator<_Tp> iterator;
	
	      typedef bidirectional_iterator_tag iterator_category;
	      typedef ptrdiff_t                  difference_type;
	
	      typedef _Rb_tree_const_iterator<_Tp>        _Self;
	      typedef _Rb_tree_node_base::_Const_Base_ptr _Base_ptr;
	      typedef const _Rb_tree_node<_Tp>*           _Link_type;
	
	      _Rb_tree_const_iterator() _GLIBCXX_NOEXCEPT
	      : _M_node() { }
	
	      explicit
	      _Rb_tree_const_iterator(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      : _M_node(__x) { }
	
	      _Rb_tree_const_iterator(const iterator& __it) _GLIBCXX_NOEXCEPT
	      : _M_node(__it._M_node) { }
	
	      iterator
	      _M_const_cast() const _GLIBCXX_NOEXCEPT
	      { return iterator(const_cast<typename iterator::_Base_ptr>(_M_node)); }
	
	      reference
	      operator*() const _GLIBCXX_NOEXCEPT
	      { return *static_cast<_Link_type>(_M_node)->_M_valptr(); }
	
	      pointer
	      operator->() const _GLIBCXX_NOEXCEPT
	      { return static_cast<_Link_type>(_M_node)->_M_valptr(); }
	
	      _Self&
	      operator++() _GLIBCXX_NOEXCEPT
	      {
		_M_node = _Rb_tree_increment(_M_node);
		return *this;
	      }
	
	      _Self
	      operator++(int) _GLIBCXX_NOEXCEPT
	      {
		_Self __tmp = *this;
		_M_node = _Rb_tree_increment(_M_node);
		return __tmp;
	      }
	
	      _Self&
	      operator--() _GLIBCXX_NOEXCEPT
	      {
		_M_node = _Rb_tree_decrement(_M_node);
		return *this;
	      }
	
	      _Self
	      operator--(int) _GLIBCXX_NOEXCEPT
	      {
		_Self __tmp = *this;
		_M_node = _Rb_tree_decrement(_M_node);
		return __tmp;
	      }
	
	      bool
	      operator==(const _Self& __x) const _GLIBCXX_NOEXCEPT
	      { return _M_node == __x._M_node; }
	
	      bool
	      operator!=(const _Self& __x) const _GLIBCXX_NOEXCEPT
	      { return _M_node != __x._M_node; }
	
	      _Base_ptr _M_node;
	    };
	
	  template<typename _Val>
	    inline bool
	    operator==(const _Rb_tree_iterator<_Val>& __x,
	               const _Rb_tree_const_iterator<_Val>& __y) _GLIBCXX_NOEXCEPT
	    { return __x._M_node == __y._M_node; }
	
	  template<typename _Val>
	    inline bool
	    operator!=(const _Rb_tree_iterator<_Val>& __x,
	               const _Rb_tree_const_iterator<_Val>& __y) _GLIBCXX_NOEXCEPT
	    { return __x._M_node != __y._M_node; }
	
	  void
	  _Rb_tree_insert_and_rebalance(const bool __insert_left,
	                                _Rb_tree_node_base* __x,
	                                _Rb_tree_node_base* __p,
	                                _Rb_tree_node_base& __header) throw ();
	
	  _Rb_tree_node_base*
	  _Rb_tree_rebalance_for_erase(_Rb_tree_node_base* const __z,
				       _Rb_tree_node_base& __header) throw ();
	
	#if __cplusplus > 201103L
	  template<typename _Cmp, typename _SfinaeType, typename = __void_t<>>
	    struct __has_is_transparent
	    { };
	
	  template<typename _Cmp, typename _SfinaeType>
	    struct __has_is_transparent<_Cmp, _SfinaeType,
					__void_t<typename _Cmp::is_transparent>>
	    { typedef void type; };
	#endif
	
	#if __cplusplus > 201402L
	  template<typename _Tree1, typename _Cmp2>
	    struct _Rb_tree_merge_helper { };
	#endif
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc = allocator<_Val> >
	    class _Rb_tree
	    {
	      typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
	        rebind<_Rb_tree_node<_Val> >::other _Node_allocator;
	
	      typedef __gnu_cxx::__alloc_traits<_Node_allocator> _Alloc_traits;
	
	    protected:
	      typedef _Rb_tree_node_base* 		_Base_ptr;
	      typedef const _Rb_tree_node_base* 	_Const_Base_ptr;
	      typedef _Rb_tree_node<_Val>* 		_Link_type;
	      typedef const _Rb_tree_node<_Val>*	_Const_Link_type;
	
	    private:
	      // Functor recycling a pool of nodes and using allocation once the pool
	      // is empty.
	      struct _Reuse_or_alloc_node
	      {
		_Reuse_or_alloc_node(_Rb_tree& __t)
		  : _M_root(__t._M_root()), _M_nodes(__t._M_rightmost()), _M_t(__t)
		{
		  if (_M_root)
		    {
		      _M_root->_M_parent = 0;
	
		      if (_M_nodes->_M_left)
			_M_nodes = _M_nodes->_M_left;
		    }
		  else
		    _M_nodes = 0;
		}
	
	#if __cplusplus >= 201103L
		_Reuse_or_alloc_node(const _Reuse_or_alloc_node&) = delete;
	#endif
	
		~_Reuse_or_alloc_node()
		{ _M_t._M_erase(static_cast<_Link_type>(_M_root)); }
	
		template<typename _Arg>
		  _Link_type
	#if __cplusplus < 201103L
		  operator()(const _Arg& __arg)
	#else
		  operator()(_Arg&& __arg)
	#endif
		  {
		    _Link_type __node = static_cast<_Link_type>(_M_extract());
		    if (__node)
		      {
			_M_t._M_destroy_node(__node);
			_M_t._M_construct_node(__node, _GLIBCXX_FORWARD(_Arg, __arg));
			return __node;
		      }
	
		    return _M_t._M_create_node(_GLIBCXX_FORWARD(_Arg, __arg));
		  }
	
	      private:
		_Base_ptr
		_M_extract()
		{
		  if (!_M_nodes)
		    return _M_nodes;
	
		  _Base_ptr __node = _M_nodes;
		  _M_nodes = _M_nodes->_M_parent;
		  if (_M_nodes)
		    {
		      if (_M_nodes->_M_right == __node)
			{
			  _M_nodes->_M_right = 0;
	
			  if (_M_nodes->_M_left)
			    {
			      _M_nodes = _M_nodes->_M_left;
	
			      while (_M_nodes->_M_right)
				_M_nodes = _M_nodes->_M_right;
	
			      if (_M_nodes->_M_left)
				_M_nodes = _M_nodes->_M_left;
			    }
			}
		      else // __node is on the left.
			_M_nodes->_M_left = 0;
		    }
		  else
		    _M_root = 0;
	
		  return __node;
		}
	
		_Base_ptr _M_root;
		_Base_ptr _M_nodes;
		_Rb_tree& _M_t;
	      };
	
	      // Functor similar to the previous one but without any pool of nodes to
	      // recycle.
	      struct _Alloc_node
	      {
		_Alloc_node(_Rb_tree& __t)
		  : _M_t(__t) { }
	
		template<typename _Arg>
		  _Link_type
	#if __cplusplus < 201103L
		  operator()(const _Arg& __arg) const
	#else
		  operator()(_Arg&& __arg) const
	#endif
		  { return _M_t._M_create_node(_GLIBCXX_FORWARD(_Arg, __arg)); }
	
	      private:
		_Rb_tree& _M_t;
	      };
	
	    public:
	      typedef _Key 				key_type;
	      typedef _Val 				value_type;
	      typedef value_type* 			pointer;
	      typedef const value_type* 		const_pointer;
	      typedef value_type& 			reference;
	      typedef const value_type& 		const_reference;
	      typedef size_t 				size_type;
	      typedef ptrdiff_t 			difference_type;
	      typedef _Alloc 				allocator_type;
	
	      _Node_allocator&
	      _M_get_Node_allocator() _GLIBCXX_NOEXCEPT
	      { return *static_cast<_Node_allocator*>(&this->_M_impl); }
	      
	      const _Node_allocator&
	      _M_get_Node_allocator() const _GLIBCXX_NOEXCEPT
	      { return *static_cast<const _Node_allocator*>(&this->_M_impl); }
	
	      allocator_type
	      get_allocator() const _GLIBCXX_NOEXCEPT
	      { return allocator_type(_M_get_Node_allocator()); }
	
	    protected:
	      _Link_type
	      _M_get_node()
	      { return _Alloc_traits::allocate(_M_get_Node_allocator(), 1); }
	
	      void
	      _M_put_node(_Link_type __p) _GLIBCXX_NOEXCEPT
	      { _Alloc_traits::deallocate(_M_get_Node_allocator(), __p, 1); }
	
	#if __cplusplus < 201103L
	      void
	      _M_construct_node(_Link_type __node, const value_type& __x)
	      {
		__try
		  { get_allocator().construct(__node->_M_valptr(), __x); }
		__catch(...)
		  {
		    _M_put_node(__node);
		    __throw_exception_again;
		  }
	      }
	
	      _Link_type
	      _M_create_node(const value_type& __x)
	      {
		_Link_type __tmp = _M_get_node();
		_M_construct_node(__tmp, __x);
		return __tmp;
	      }
	
	      void
	      _M_destroy_node(_Link_type __p)
	      { get_allocator().destroy(__p->_M_valptr()); }
	#else
	      template<typename... _Args>
		void
		_M_construct_node(_Link_type __node, _Args&&... __args)
		{
		  __try
		    {
		      ::new(__node) _Rb_tree_node<_Val>;
		      _Alloc_traits::construct(_M_get_Node_allocator(),
					       __node->_M_valptr(),
					       std::forward<_Args>(__args)...);
		    }
		  __catch(...)
		    {
		      __node->~_Rb_tree_node<_Val>();
		      _M_put_node(__node);
		      __throw_exception_again;
		    }
		}
	
	      template<typename... _Args>
	        _Link_type
	        _M_create_node(_Args&&... __args)
		{
		  _Link_type __tmp = _M_get_node();
		  _M_construct_node(__tmp, std::forward<_Args>(__args)...);
		  return __tmp;
		}
	
	      void
	      _M_destroy_node(_Link_type __p) noexcept
	      {
		_Alloc_traits::destroy(_M_get_Node_allocator(), __p->_M_valptr());
		__p->~_Rb_tree_node<_Val>();
	      }
	#endif
	
	      void
	      _M_drop_node(_Link_type __p) _GLIBCXX_NOEXCEPT
	      {
		_M_destroy_node(__p);
		_M_put_node(__p);
	      }
	
	      template<typename _NodeGen>
		_Link_type
		_M_clone_node(_Const_Link_type __x, _NodeGen& __node_gen)
		{
		  _Link_type __tmp = __node_gen(*__x->_M_valptr());
		  __tmp->_M_color = __x->_M_color;
		  __tmp->_M_left = 0;
		  __tmp->_M_right = 0;
		  return __tmp;
		}
	
	    protected:
	      // Unused _Is_pod_comparator is kept as it is part of mangled name.
	      template<typename _Key_compare,
		       bool /* _Is_pod_comparator */ = __is_pod(_Key_compare)>

	        struct _Rb_tree_impl
		: public _Node_allocator
		, public _Rb_tree_key_compare<_Key_compare>
		, public _Rb_tree_header
	        {
		  typedef _Rb_tree_key_compare<_Key_compare> _Base_key_compare;
	
	#if __cplusplus < 201103L
		  _Rb_tree_impl()
		  { }
	#else
		  _Rb_tree_impl() = default;
		  _Rb_tree_impl(_Rb_tree_impl&&) = default;
	#endif
	

		  _Rb_tree_impl(const _Rb_tree_impl& __x)
		  : _Node_allocator(_Alloc_traits::_S_select_on_copy(__x))
		  , _Base_key_compare(__x._M_key_compare)
		  { }
	
	#if __cplusplus < 201103L
		  _Rb_tree_impl(const _Key_compare& __comp, const _Node_allocator& __a)
		  : _Node_allocator(__a), _Base_key_compare(__comp)
		  { }
	#else
		  _Rb_tree_impl(const _Key_compare& __comp, _Node_allocator&& __a)
		  : _Node_allocator(std::move(__a)), _Base_key_compare(__comp)
		  { }
	#endif
		};
	
	      _Rb_tree_impl<_Compare> _M_impl;
	
	    protected:
	      _Base_ptr&
	      _M_root() _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_parent; }
	
	      _Const_Base_ptr
	      _M_root() const _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_parent; }
	
	      _Base_ptr&
	      _M_leftmost() _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_left; }
	
	      _Const_Base_ptr
	      _M_leftmost() const _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_left; }
	
	      _Base_ptr&
	      _M_rightmost() _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_right; }
	
	      _Const_Base_ptr
	      _M_rightmost() const _GLIBCXX_NOEXCEPT
	      { return this->_M_impl._M_header._M_right; }
	
	      _Link_type
	      _M_begin() _GLIBCXX_NOEXCEPT
	      { return static_cast<_Link_type>(this->_M_impl._M_header._M_parent); }
	
	      _Const_Link_type
	      _M_begin() const _GLIBCXX_NOEXCEPT
	      {
		return static_cast<_Const_Link_type>
		  (this->_M_impl._M_header._M_parent);
	      }
	
	      _Base_ptr
	      _M_end() _GLIBCXX_NOEXCEPT
	      { return &this->_M_impl._M_header; }
	
	      _Const_Base_ptr
	      _M_end() const _GLIBCXX_NOEXCEPT
	      { return &this->_M_impl._M_header; }
	
	      static const_reference
	      _S_value(_Const_Link_type __x)
	      { return *__x->_M_valptr(); }
	
	      static const _Key&
	      _S_key(_Const_Link_type __x)
	      { return _KeyOfValue()(_S_value(__x)); }
	
	      static _Link_type
	      _S_left(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return static_cast<_Link_type>(__x->_M_left); }
	
	      static _Const_Link_type
	      _S_left(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return static_cast<_Const_Link_type>(__x->_M_left); }
	
	      static _Link_type
	      _S_right(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return static_cast<_Link_type>(__x->_M_right); }
	
	      static _Const_Link_type
	      _S_right(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return static_cast<_Const_Link_type>(__x->_M_right); }
	
	      static const_reference
	      _S_value(_Const_Base_ptr __x)
	      { return *static_cast<_Const_Link_type>(__x)->_M_valptr(); }
	
	      static const _Key&
	      _S_key(_Const_Base_ptr __x)
	      { return _KeyOfValue()(_S_value(__x)); }
	
	      static _Base_ptr
	      _S_minimum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return _Rb_tree_node_base::_S_minimum(__x); }
	
	      static _Const_Base_ptr
	      _S_minimum(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return _Rb_tree_node_base::_S_minimum(__x); }
	
	      static _Base_ptr
	      _S_maximum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return _Rb_tree_node_base::_S_maximum(__x); }
	
	      static _Const_Base_ptr
	      _S_maximum(_Const_Base_ptr __x) _GLIBCXX_NOEXCEPT
	      { return _Rb_tree_node_base::_S_maximum(__x); }
	
	    public:
	      typedef _Rb_tree_iterator<value_type>       iterator;
	      typedef _Rb_tree_const_iterator<value_type> const_iterator;
	
	      typedef std::reverse_iterator<iterator>       reverse_iterator;
	      typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
	
	#if __cplusplus > 201402L
	      using node_type = _Node_handle<_Key, _Val, _Node_allocator>;
	      using insert_return_type = _Node_insert_return<
		conditional_t<is_same_v<_Key, _Val>, const_iterator, iterator>,
		node_type>;
	#endif
	
	      pair<_Base_ptr, _Base_ptr>
	      _M_get_insert_unique_pos(const key_type& __k);
	
	      pair<_Base_ptr, _Base_ptr>
	      _M_get_insert_equal_pos(const key_type& __k);
	
	      pair<_Base_ptr, _Base_ptr>
	      _M_get_insert_hint_unique_pos(const_iterator __pos,
					    const key_type& __k);
	
	      pair<_Base_ptr, _Base_ptr>
	      _M_get_insert_hint_equal_pos(const_iterator __pos,
					   const key_type& __k);
	
	    private:
	#if __cplusplus >= 201103L
	      template<typename _Arg, typename _NodeGen>
	        iterator
		_M_insert_(_Base_ptr __x, _Base_ptr __y, _Arg&& __v, _NodeGen&);
	
	      iterator
	      _M_insert_node(_Base_ptr __x, _Base_ptr __y, _Link_type __z);
	
	      template<typename _Arg>
	        iterator
	        _M_insert_lower(_Base_ptr __y, _Arg&& __v);
	
	      template<typename _Arg>
	        iterator
	        _M_insert_equal_lower(_Arg&& __x);
	
	      iterator
	      _M_insert_lower_node(_Base_ptr __p, _Link_type __z);
	
	      iterator
	      _M_insert_equal_lower_node(_Link_type __z);
	#else
	      template<typename _NodeGen>
		iterator
		_M_insert_(_Base_ptr __x, _Base_ptr __y,
			   const value_type& __v, _NodeGen&);
	
	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
	      // 233. Insertion hints in associative containers.
	      iterator
	      _M_insert_lower(_Base_ptr __y, const value_type& __v);
	
	      iterator
	      _M_insert_equal_lower(const value_type& __x);
	#endif
	
	      template<typename _NodeGen>
		_Link_type
		_M_copy(_Const_Link_type __x, _Base_ptr __p, _NodeGen&);
	
	      template<typename _NodeGen>
		_Link_type
		_M_copy(const _Rb_tree& __x, _NodeGen& __gen)
		{
		  _Link_type __root = _M_copy(__x._M_begin(), _M_end(), __gen);
		  _M_leftmost() = _S_minimum(__root);
		  _M_rightmost() = _S_maximum(__root);
		  _M_impl._M_node_count = __x._M_impl._M_node_count;
		  return __root;
		}
	
	      _Link_type
	      _M_copy(const _Rb_tree& __x)
	      {
		_Alloc_node __an(*this);
		return _M_copy(__x, __an);
	      }
	
	      void
	      _M_erase(_Link_type __x);
	
	      iterator
	      _M_lower_bound(_Link_type __x, _Base_ptr __y,
			     const _Key& __k);
	
	      const_iterator
	      _M_lower_bound(_Const_Link_type __x, _Const_Base_ptr __y,
			     const _Key& __k) const;
	
	      iterator
	      _M_upper_bound(_Link_type __x, _Base_ptr __y,
			     const _Key& __k);
	
	      const_iterator
	      _M_upper_bound(_Const_Link_type __x, _Const_Base_ptr __y,
			     const _Key& __k) const;
	
	    public:
	      // allocation/deallocation
	#if __cplusplus < 201103L
	      _Rb_tree() { }
	#else
	      _Rb_tree() = default;
	#endif
	
	      _Rb_tree(const _Compare& __comp,
		       const allocator_type& __a = allocator_type())
	      : _M_impl(__comp, _Node_allocator(__a)) { }
	
	      _Rb_tree(const _Rb_tree& __x)
	      : _M_impl(__x._M_impl)
	      {
		if (__x._M_root() != 0)
		  _M_root() = _M_copy(__x);
	      }
	
	#if __cplusplus >= 201103L
	      _Rb_tree(const allocator_type& __a)
	      : _M_impl(_Compare(), _Node_allocator(__a))
	      { }
	
	      _Rb_tree(const _Rb_tree& __x, const allocator_type& __a)
	      : _M_impl(__x._M_impl._M_key_compare, _Node_allocator(__a))
	      {
		if (__x._M_root() != nullptr)
		  _M_root() = _M_copy(__x);
	      }
	
	      _Rb_tree(_Rb_tree&&) = default;
	
	      _Rb_tree(_Rb_tree&& __x, const allocator_type& __a)
	      : _Rb_tree(std::move(__x), _Node_allocator(__a))
	      { }
	
	      _Rb_tree(_Rb_tree&& __x, _Node_allocator&& __a);
	#endif
	
	      ~_Rb_tree() _GLIBCXX_NOEXCEPT
	      { _M_erase(_M_begin()); }
	
	      _Rb_tree&
	      operator=(const _Rb_tree& __x);
	
	      // Accessors.
	      _Compare
	      key_comp() const
	      { return _M_impl._M_key_compare; }
	
	      iterator
	      begin() _GLIBCXX_NOEXCEPT
	      { return iterator(this->_M_impl._M_header._M_left); }
	
	      const_iterator
	      begin() const _GLIBCXX_NOEXCEPT
	      { return const_iterator(this->_M_impl._M_header._M_left); }
	
	      iterator
	      end() _GLIBCXX_NOEXCEPT
	      { return iterator(&this->_M_impl._M_header); }
	
	      const_iterator
	      end() const _GLIBCXX_NOEXCEPT
	      { return const_iterator(&this->_M_impl._M_header); }
	
	      reverse_iterator
	      rbegin() _GLIBCXX_NOEXCEPT
	      { return reverse_iterator(end()); }
	
	      const_reverse_iterator
	      rbegin() const _GLIBCXX_NOEXCEPT
	      { return const_reverse_iterator(end()); }
	
	      reverse_iterator
	      rend() _GLIBCXX_NOEXCEPT
	      { return reverse_iterator(begin()); }
	
	      const_reverse_iterator
	      rend() const _GLIBCXX_NOEXCEPT
	      { return const_reverse_iterator(begin()); }
	
	      bool
	      empty() const _GLIBCXX_NOEXCEPT
	      { return _M_impl._M_node_count == 0; }
	
	      size_type
	      size() const _GLIBCXX_NOEXCEPT 
	      { return _M_impl._M_node_count; }
	
	      size_type
	      max_size() const _GLIBCXX_NOEXCEPT
	      { return _Alloc_traits::max_size(_M_get_Node_allocator()); }
	
	      void
	      swap(_Rb_tree& __t)
	      _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Compare>::value);
	
	      // Insert/erase.
	#if __cplusplus >= 201103L
	      template<typename _Arg>
	        pair<iterator, bool>
	        _M_insert_unique(_Arg&& __x);
	
	      template<typename _Arg>
	        iterator
	        _M_insert_equal(_Arg&& __x);
	
	      template<typename _Arg, typename _NodeGen>
	        iterator
		_M_insert_unique_(const_iterator __pos, _Arg&& __x, _NodeGen&);
	
	      template<typename _Arg>
		iterator
		_M_insert_unique_(const_iterator __pos, _Arg&& __x)
		{
		  _Alloc_node __an(*this);
		  return _M_insert_unique_(__pos, std::forward<_Arg>(__x), __an);
		}
	
	      template<typename _Arg, typename _NodeGen>
		iterator
		_M_insert_equal_(const_iterator __pos, _Arg&& __x, _NodeGen&);
	
	      template<typename _Arg>
		iterator
		_M_insert_equal_(const_iterator __pos, _Arg&& __x)
		{
		  _Alloc_node __an(*this);
		  return _M_insert_equal_(__pos, std::forward<_Arg>(__x), __an);
		}
	
	      template<typename... _Args>
		pair<iterator, bool>
		_M_emplace_unique(_Args&&... __args);
	
	      template<typename... _Args>
		iterator
		_M_emplace_equal(_Args&&... __args);
	
	      template<typename... _Args>
		iterator
		_M_emplace_hint_unique(const_iterator __pos, _Args&&... __args);
	
	      template<typename... _Args>
		iterator
		_M_emplace_hint_equal(const_iterator __pos, _Args&&... __args);
	#else
	      pair<iterator, bool>
	      _M_insert_unique(const value_type& __x);
	
	      iterator
	      _M_insert_equal(const value_type& __x);
	
	      template<typename _NodeGen>
		iterator
		_M_insert_unique_(const_iterator __pos, const value_type& __x,
				  _NodeGen&);
	
	      iterator
	      _M_insert_unique_(const_iterator __pos, const value_type& __x)
	      {
		_Alloc_node __an(*this);
		return _M_insert_unique_(__pos, __x, __an);
	      }
	
	      template<typename _NodeGen>
		iterator
		_M_insert_equal_(const_iterator __pos, const value_type& __x,
				 _NodeGen&);
	      iterator
	      _M_insert_equal_(const_iterator __pos, const value_type& __x)
	      {
		_Alloc_node __an(*this);
		return _M_insert_equal_(__pos, __x, __an);
	      }
	#endif
	
	      template<typename _InputIterator>
	        void
	        _M_insert_unique(_InputIterator __first, _InputIterator __last);
	
	      template<typename _InputIterator>
	        void
	        _M_insert_equal(_InputIterator __first, _InputIterator __last);
	
	    private:
	      void
	      _M_erase_aux(const_iterator __position);
	
	      void
	      _M_erase_aux(const_iterator __first, const_iterator __last);
	
	    public:
	#if __cplusplus >= 201103L
	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
	      // DR 130. Associative erase should return an iterator.
	      _GLIBCXX_ABI_TAG_CXX11
	      iterator
	      erase(const_iterator __position)
	      {
		__glibcxx_assert(__position != end());
		const_iterator __result = __position;
		++__result;
		_M_erase_aux(__position);
		return __result._M_const_cast();
	      }
	
	      // LWG 2059.
	      _GLIBCXX_ABI_TAG_CXX11
	      iterator
	      erase(iterator __position)
	      {
		__glibcxx_assert(__position != end());
		iterator __result = __position;
		++__result;
		_M_erase_aux(__position);
		return __result;
	      }
	#else
	      void
	      erase(iterator __position)
	      {
		__glibcxx_assert(__position != end());
		_M_erase_aux(__position);
	      }
	
	      void
	      erase(const_iterator __position)
	      {
		__glibcxx_assert(__position != end());
		_M_erase_aux(__position);
	      }
	#endif
	      size_type
	      erase(const key_type& __x);
	
	#if __cplusplus >= 201103L
	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
	      // DR 130. Associative erase should return an iterator.
	      _GLIBCXX_ABI_TAG_CXX11
	      iterator
	      erase(const_iterator __first, const_iterator __last)
	      {
		_M_erase_aux(__first, __last);
		return __last._M_const_cast();
	      }
	#else
	      void
	      erase(iterator __first, iterator __last)
	      { _M_erase_aux(__first, __last); }
	
	      void
	      erase(const_iterator __first, const_iterator __last)
	      { _M_erase_aux(__first, __last); }
	#endif
	      void
	      erase(const key_type* __first, const key_type* __last);
	
	      void
	      clear() _GLIBCXX_NOEXCEPT
	      {
	        _M_erase(_M_begin());
		_M_impl._M_reset();
	      }
	
	      // Set operations.
	      iterator
	      find(const key_type& __k);
	
	      const_iterator
	      find(const key_type& __k) const;
	
	      size_type
	      count(const key_type& __k) const;
	
	      iterator
	      lower_bound(const key_type& __k)
	      { return _M_lower_bound(_M_begin(), _M_end(), __k); }
	
	      const_iterator
	      lower_bound(const key_type& __k) const
	      { return _M_lower_bound(_M_begin(), _M_end(), __k); }
	
	      iterator
	      upper_bound(const key_type& __k)
	      { return _M_upper_bound(_M_begin(), _M_end(), __k); }
	
	      const_iterator
	      upper_bound(const key_type& __k) const
	      { return _M_upper_bound(_M_begin(), _M_end(), __k); }
	
	      pair<iterator, iterator>
	      equal_range(const key_type& __k);
	
	      pair<const_iterator, const_iterator>
	      equal_range(const key_type& __k) const;
	
	#if __cplusplus > 201103L
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		iterator
		_M_find_tr(const _Kt& __k)
		{
		  const _Rb_tree* __const_this = this;
		  return __const_this->_M_find_tr(__k)._M_const_cast();
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		const_iterator
		_M_find_tr(const _Kt& __k) const
		{
		  auto __j = _M_lower_bound_tr(__k);
		  if (__j != end() && _M_impl._M_key_compare(__k, _S_key(__j._M_node)))
		    __j = end();
		  return __j;
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		size_type
		_M_count_tr(const _Kt& __k) const
		{
		  auto __p = _M_equal_range_tr(__k);
		  return std::distance(__p.first, __p.second);
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		iterator
		_M_lower_bound_tr(const _Kt& __k)
		{
		  const _Rb_tree* __const_this = this;
		  return __const_this->_M_lower_bound_tr(__k)._M_const_cast();
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		const_iterator
		_M_lower_bound_tr(const _Kt& __k) const
		{
		  auto __x = _M_begin();
		  auto __y = _M_end();
		  while (__x != 0)
		    if (!_M_impl._M_key_compare(_S_key(__x), __k))
		      {
			__y = __x;
			__x = _S_left(__x);
		      }
		    else
		      __x = _S_right(__x);
		  return const_iterator(__y);
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		iterator
		_M_upper_bound_tr(const _Kt& __k)
		{
		  const _Rb_tree* __const_this = this;
		  return __const_this->_M_upper_bound_tr(__k)._M_const_cast();
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		const_iterator
		_M_upper_bound_tr(const _Kt& __k) const
		{
		  auto __x = _M_begin();
		  auto __y = _M_end();
		  while (__x != 0)
		    if (_M_impl._M_key_compare(__k, _S_key(__x)))
		      {
			__y = __x;
			__x = _S_left(__x);
		      }
		    else
		      __x = _S_right(__x);
		  return const_iterator(__y);
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		pair<iterator, iterator>
		_M_equal_range_tr(const _Kt& __k)
		{
		  const _Rb_tree* __const_this = this;
		  auto __ret = __const_this->_M_equal_range_tr(__k);
		  return { __ret.first._M_const_cast(), __ret.second._M_const_cast() };
		}
	
	      template<typename _Kt,
		       typename _Req =
			 typename __has_is_transparent<_Compare, _Kt>::type>
		pair<const_iterator, const_iterator>
		_M_equal_range_tr(const _Kt& __k) const
		{
		  auto __low = _M_lower_bound_tr(__k);
		  auto __high = __low;
		  auto& __cmp = _M_impl._M_key_compare;
		  while (__high != end() && !__cmp(__k, _S_key(__high._M_node)))
		    ++__high;
		  return { __low, __high };
		}
	#endif
	
	      // Debugging.
	      bool
	      __rb_verify() const;
	
	#if __cplusplus >= 201103L
	      _Rb_tree&
	      operator=(_Rb_tree&&)
	      noexcept(_Alloc_traits::_S_nothrow_move()
		       && is_nothrow_move_assignable<_Compare>::value);
	
	      template<typename _Iterator>
		void
		_M_assign_unique(_Iterator, _Iterator);
	
	      template<typename _Iterator>
		void
		_M_assign_equal(_Iterator, _Iterator);
	
	    private:
	      // Move elements from container with equal allocator.
	      void
	      _M_move_data(_Rb_tree& __x, std::true_type)
	      { _M_impl._M_move_data(__x._M_impl); }
	
	      // Move elements from container with possibly non-equal allocator,
	      // which might result in a copy not a move.
	      void
	      _M_move_data(_Rb_tree&, std::false_type);
	
	      // Move assignment from container with equal allocator.
	      void
	      _M_move_assign(_Rb_tree&, std::true_type);
	
	      // Move assignment from container with possibly non-equal allocator,
	      // which might result in a copy not a move.
	      void
	      _M_move_assign(_Rb_tree&, std::false_type);
	#endif
	
	#if __cplusplus > 201402L
	    public:
	      /// Re-insert an extracted node.
	      insert_return_type
	      _M_reinsert_node_unique(node_type&& __nh)
	      {
		insert_return_type __ret;
		if (__nh.empty())
		  __ret.position = end();
		else
		  {
		    __glibcxx_assert(_M_get_Node_allocator() == *__nh._M_alloc);
	
		    auto __res = _M_get_insert_unique_pos(__nh._M_key());
		    if (__res.second)
		      {
			__ret.position
			  = _M_insert_node(__res.first, __res.second, __nh._M_ptr);
			__nh._M_ptr = nullptr;
			__ret.inserted = true;
		      }
		    else
		      {
			__ret.node = std::move(__nh);
			__ret.position = iterator(__res.first);
			__ret.inserted = false;
		      }
		  }
		return __ret;
	      }
	
	      /// Re-insert an extracted node.
	      iterator
	      _M_reinsert_node_equal(node_type&& __nh)
	      {
		iterator __ret;
		if (__nh.empty())
		  __ret = end();
		else
		  {
		    __glibcxx_assert(_M_get_Node_allocator() == *__nh._M_alloc);
		    auto __res = _M_get_insert_equal_pos(__nh._M_key());
		    if (__res.second)
		      __ret = _M_insert_node(__res.first, __res.second, __nh._M_ptr);
		    else
		      __ret = _M_insert_equal_lower_node(__nh._M_ptr);
		    __nh._M_ptr = nullptr;
		  }
		return __ret;
	      }
	
	      /// Re-insert an extracted node.
	      iterator
	      _M_reinsert_node_hint_unique(const_iterator __hint, node_type&& __nh)
	      {
		iterator __ret;
		if (__nh.empty())
		  __ret = end();
		else
		  {
		    __glibcxx_assert(_M_get_Node_allocator() == *__nh._M_alloc);
		    auto __res = _M_get_insert_hint_unique_pos(__hint, __nh._M_key());
		    if (__res.second)
		      {
			__ret = _M_insert_node(__res.first, __res.second, __nh._M_ptr);
			__nh._M_ptr = nullptr;
		      }
		    else
		      __ret = iterator(__res.first);
		  }
		return __ret;
	      }
	
	      /// Re-insert an extracted node.
	      iterator
	      _M_reinsert_node_hint_equal(const_iterator __hint, node_type&& __nh)
	      {
		iterator __ret;
		if (__nh.empty())
		  __ret = end();
		else
		  {
		    __glibcxx_assert(_M_get_Node_allocator() == *__nh._M_alloc);
		    auto __res = _M_get_insert_hint_equal_pos(__hint, __nh._M_key());
		    if (__res.second)
		      __ret = _M_insert_node(__res.first, __res.second, __nh._M_ptr);
		    else
		      __ret = _M_insert_equal_lower_node(__nh._M_ptr);
		    __nh._M_ptr = nullptr;
		  }
		return __ret;
	      }
	
	      /// Extract a node.
	      node_type
	      extract(const_iterator __pos)
	      {
		auto __ptr = _Rb_tree_rebalance_for_erase(
		    __pos._M_const_cast()._M_node, _M_impl._M_header);
		--_M_impl._M_node_count;
		return { static_cast<_Link_type>(__ptr), _M_get_Node_allocator() };
	      }
	
	      /// Extract a node.
	      node_type
	      extract(const key_type& __k)
	      {
		node_type __nh;
		auto __pos = find(__k);
		if (__pos != end())
		  __nh = extract(const_iterator(__pos));
		return __nh;
	      }
	
	      template<typename _Compare2>
		using _Compatible_tree
		  = _Rb_tree<_Key, _Val, _KeyOfValue, _Compare2, _Alloc>;
	
	      template<typename, typename>
		friend class _Rb_tree_merge_helper;
	
	      /// Merge from a compatible container into one with unique keys.
	      template<typename _Compare2>
		void
		_M_merge_unique(_Compatible_tree<_Compare2>& __src) noexcept
		{
		  using _Merge_helper = _Rb_tree_merge_helper<_Rb_tree, _Compare2>;
		  for (auto __i = __src.begin(), __end = __src.end(); __i != __end;)
		    {
		      auto __pos = __i++;
		      auto __res = _M_get_insert_unique_pos(_KeyOfValue()(*__pos));
		      if (__res.second)
			{
			  auto& __src_impl = _Merge_helper::_S_get_impl(__src);
			  auto __ptr = _Rb_tree_rebalance_for_erase(
			      __pos._M_node, __src_impl._M_header);
			  --__src_impl._M_node_count;
			  _M_insert_node(__res.first, __res.second,
					 static_cast<_Link_type>(__ptr));
			}
		    }
		}
	
	      /// Merge from a compatible container into one with equivalent keys.
	      template<typename _Compare2>
		void
		_M_merge_equal(_Compatible_tree<_Compare2>& __src) noexcept
		{
		  using _Merge_helper = _Rb_tree_merge_helper<_Rb_tree, _Compare2>;
		  for (auto __i = __src.begin(), __end = __src.end(); __i != __end;)
		    {
		      auto __pos = __i++;
		      auto __res = _M_get_insert_equal_pos(_KeyOfValue()(*__pos));
		      if (__res.second)
			{
			  auto& __src_impl = _Merge_helper::_S_get_impl(__src);
			  auto __ptr = _Rb_tree_rebalance_for_erase(
			      __pos._M_node, __src_impl._M_header);
			  --__src_impl._M_node_count;
			  _M_insert_node(__res.first, __res.second,
					 static_cast<_Link_type>(__ptr));
			}
		    }
		}
	#endif // C++17
	    };
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator==(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		       const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    {
	      return __x.size() == __y.size()
		     && std::equal(__x.begin(), __x.end(), __y.begin());
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator<(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		      const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    {
	      return std::lexicographical_compare(__x.begin(), __x.end(), 
						  __y.begin(), __y.end());
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator!=(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		       const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    { return !(__x == __y); }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator>(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		      const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    { return __y < __x; }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator<=(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		       const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    { return !(__y < __x); }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline bool
	    operator>=(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		       const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    { return !(__x < __y); }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline void
	    swap(_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __x,
		 _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>& __y)
	    { __x.swap(__y); }
	
	#if __cplusplus >= 201103L
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _Rb_tree(_Rb_tree&& __x, _Node_allocator&& __a)
	    : _M_impl(__x._M_impl._M_key_compare, std::move(__a))
	    {
	      using __eq = typename _Alloc_traits::is_always_equal;
	      if (__x._M_root() != nullptr)
		_M_move_data(__x, __eq());
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_move_data(_Rb_tree& __x, std::false_type)
	    {
	      if (_M_get_Node_allocator() == __x._M_get_Node_allocator())
		_M_move_data(__x, std::true_type());
	      else
		{
		  _Alloc_node __an(*this);
		  auto __lbd =
		    [&__an](const value_type& __cval)
		    {
		      auto& __val = const_cast<value_type&>(__cval);
		      return __an(std::move_if_noexcept(__val));
		    };
		  _M_root() = _M_copy(__x, __lbd);
		}
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_move_assign(_Rb_tree& __x, true_type)
	    {
	      clear();
	      if (__x._M_root() != nullptr)
		_M_move_data(__x, std::true_type());
	      std::__alloc_on_move(_M_get_Node_allocator(),
				   __x._M_get_Node_allocator());
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_move_assign(_Rb_tree& __x, false_type)
	    {
	      if (_M_get_Node_allocator() == __x._M_get_Node_allocator())
		return _M_move_assign(__x, true_type{});
	
	      // Try to move each node reusing existing nodes and copying __x nodes
	      // structure.
	      _Reuse_or_alloc_node __roan(*this);
	      _M_impl._M_reset();
	      if (__x._M_root() != nullptr)
		{
		  auto __lbd =
		    [&__roan](const value_type& __cval)
		    {
		      auto& __val = const_cast<value_type&>(__cval);
		      return __roan(std::move_if_noexcept(__val));
		    };
		  _M_root() = _M_copy(__x, __lbd);
		  __x.clear();
		}
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    inline _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    operator=(_Rb_tree&& __x)
	    noexcept(_Alloc_traits::_S_nothrow_move()
		     && is_nothrow_move_assignable<_Compare>::value)
	    {
	      _M_impl._M_key_compare = std::move(__x._M_impl._M_key_compare);
	      _M_move_assign(__x, __bool_constant<_Alloc_traits::_S_nothrow_move()>());
	      return *this;
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename _Iterator>
	      void
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_assign_unique(_Iterator __first, _Iterator __last)
	      {
		_Reuse_or_alloc_node __roan(*this);
		_M_impl._M_reset();
		for (; __first != __last; ++__first)
		  _M_insert_unique_(end(), *__first, __roan);
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename _Iterator>
	      void
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_assign_equal(_Iterator __first, _Iterator __last)
	      {
		_Reuse_or_alloc_node __roan(*this);
		_M_impl._M_reset();
		for (; __first != __last; ++__first)
		  _M_insert_equal_(end(), *__first, __roan);
	      }
	#endif
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    operator=(const _Rb_tree& __x)
	    {
	      if (this != &__x)
		{
		  // Note that _Key may be a constant type.
	#if __cplusplus >= 201103L
		  if (_Alloc_traits::_S_propagate_on_copy_assign())
		    {
		      auto& __this_alloc = this->_M_get_Node_allocator();
		      auto& __that_alloc = __x._M_get_Node_allocator();
		      if (!_Alloc_traits::_S_always_equal()
			  && __this_alloc != __that_alloc)
			{
			  // Replacement allocator cannot free existing storage, we need
			  // to erase nodes first.
			  clear();
			  std::__alloc_on_copy(__this_alloc, __that_alloc);
			}
		    }
	#endif
	
		  _Reuse_or_alloc_node __roan(*this);
		  _M_impl._M_reset();
		  _M_impl._M_key_compare = __x._M_impl._M_key_compare;
		  if (__x._M_root() != 0)
		    _M_root() = _M_copy(__x, __roan);
		}
	
	      return *this;
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg, typename _NodeGen>
	#else
	    template<typename _NodeGen>
	#endif
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_insert_(_Base_ptr __x, _Base_ptr __p,
	#if __cplusplus >= 201103L
			 _Arg&& __v,
	#else
			 const _Val& __v,
	#endif
			 _NodeGen& __node_gen)
	      {
		bool __insert_left = (__x != 0 || __p == _M_end()
				      || _M_impl._M_key_compare(_KeyOfValue()(__v),
								_S_key(__p)));
	
		_Link_type __z = __node_gen(_GLIBCXX_FORWARD(_Arg, __v));
	
		_Rb_tree_insert_and_rebalance(__insert_left, __z, __p,
					      this->_M_impl._M_header);
		++_M_impl._M_node_count;
		return iterator(__z);
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg>
	#endif
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	#if __cplusplus >= 201103L
	    _M_insert_lower(_Base_ptr __p, _Arg&& __v)
	#else
	    _M_insert_lower(_Base_ptr __p, const _Val& __v)
	#endif
	    {
	      bool __insert_left = (__p == _M_end()
				    || !_M_impl._M_key_compare(_S_key(__p),
							       _KeyOfValue()(__v)));
	
	      _Link_type __z = _M_create_node(_GLIBCXX_FORWARD(_Arg, __v));
	
	      _Rb_tree_insert_and_rebalance(__insert_left, __z, __p,
					    this->_M_impl._M_header);
	      ++_M_impl._M_node_count;
	      return iterator(__z);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg>
	#endif
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	#if __cplusplus >= 201103L
	    _M_insert_equal_lower(_Arg&& __v)
	#else
	    _M_insert_equal_lower(const _Val& __v)
	#endif
	    {
	      _Link_type __x = _M_begin();
	      _Base_ptr __y = _M_end();
	      while (__x != 0)
		{
		  __y = __x;
		  __x = !_M_impl._M_key_compare(_S_key(__x), _KeyOfValue()(__v)) ?
		        _S_left(__x) : _S_right(__x);
		}
	      return _M_insert_lower(__y, _GLIBCXX_FORWARD(_Arg, __v));
	    }
	
	  template<typename _Key, typename _Val, typename _KoV,
		   typename _Compare, typename _Alloc>
	    template<typename _NodeGen>
	      typename _Rb_tree<_Key, _Val, _KoV, _Compare, _Alloc>::_Link_type
	      _Rb_tree<_Key, _Val, _KoV, _Compare, _Alloc>::
	      _M_copy(_Const_Link_type __x, _Base_ptr __p, _NodeGen& __node_gen)
	      {
		// Structural copy. __x and __p must be non-null.
		_Link_type __top = _M_clone_node(__x, __node_gen);
		__top->_M_parent = __p;
	
		__try
		  {
		    if (__x->_M_right)
		      __top->_M_right = _M_copy(_S_right(__x), __top, __node_gen);
		    __p = __top;
		    __x = _S_left(__x);
	
		    while (__x != 0)
		      {
			_Link_type __y = _M_clone_node(__x, __node_gen);
			__p->_M_left = __y;
			__y->_M_parent = __p;
			if (__x->_M_right)
			  __y->_M_right = _M_copy(_S_right(__x), __y, __node_gen);
			__p = __y;
			__x = _S_left(__x);
		      }
		  }
		__catch(...)
		  {
		    _M_erase(__top);
		    __throw_exception_again;
		  }
		return __top;
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_erase(_Link_type __x)
	    {
	      // Erase without rebalancing.
	      while (__x != 0)
		{
		  _M_erase(_S_right(__x));
		  _Link_type __y = _S_left(__x);
		  _M_drop_node(__x);
		  __x = __y;
		}
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_lower_bound(_Link_type __x, _Base_ptr __y,
			   const _Key& __k)
	    {
	      while (__x != 0)
		if (!_M_impl._M_key_compare(_S_key(__x), __k))
		  __y = __x, __x = _S_left(__x);
		else
		  __x = _S_right(__x);
	      return iterator(__y);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::const_iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_lower_bound(_Const_Link_type __x, _Const_Base_ptr __y,
			   const _Key& __k) const
	    {
	      while (__x != 0)
		if (!_M_impl._M_key_compare(_S_key(__x), __k))
		  __y = __x, __x = _S_left(__x);
		else
		  __x = _S_right(__x);
	      return const_iterator(__y);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_upper_bound(_Link_type __x, _Base_ptr __y,
			   const _Key& __k)
	    {
	      while (__x != 0)
		if (_M_impl._M_key_compare(__k, _S_key(__x)))
		  __y = __x, __x = _S_left(__x);
		else
		  __x = _S_right(__x);
	      return iterator(__y);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::const_iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_upper_bound(_Const_Link_type __x, _Const_Base_ptr __y,
			   const _Key& __k) const
	    {
	      while (__x != 0)
		if (_M_impl._M_key_compare(__k, _S_key(__x)))
		  __y = __x, __x = _S_left(__x);
		else
		  __x = _S_right(__x);
	      return const_iterator(__y);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::iterator,
		 typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::iterator>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    equal_range(const _Key& __k)
	    {
	      _Link_type __x = _M_begin();
	      _Base_ptr __y = _M_end();
	      while (__x != 0)
		{
		  if (_M_impl._M_key_compare(_S_key(__x), __k))
		    __x = _S_right(__x);
		  else if (_M_impl._M_key_compare(__k, _S_key(__x)))
		    __y = __x, __x = _S_left(__x);
		  else
		    {
		      _Link_type __xu(__x);
		      _Base_ptr __yu(__y);
		      __y = __x, __x = _S_left(__x);
		      __xu = _S_right(__xu);
		      return pair<iterator,
			          iterator>(_M_lower_bound(__x, __y, __k),
					    _M_upper_bound(__xu, __yu, __k));
		    }
		}
	      return pair<iterator, iterator>(iterator(__y),
					      iterator(__y));
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::const_iterator,
		 typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::const_iterator>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    equal_range(const _Key& __k) const
	    {
	      _Const_Link_type __x = _M_begin();
	      _Const_Base_ptr __y = _M_end();
	      while (__x != 0)
		{
		  if (_M_impl._M_key_compare(_S_key(__x), __k))
		    __x = _S_right(__x);
		  else if (_M_impl._M_key_compare(__k, _S_key(__x)))
		    __y = __x, __x = _S_left(__x);
		  else
		    {
		      _Const_Link_type __xu(__x);
		      _Const_Base_ptr __yu(__y);
		      __y = __x, __x = _S_left(__x);
		      __xu = _S_right(__xu);
		      return pair<const_iterator,
			          const_iterator>(_M_lower_bound(__x, __y, __k),
						  _M_upper_bound(__xu, __yu, __k));
		    }
		}
	      return pair<const_iterator, const_iterator>(const_iterator(__y),
							  const_iterator(__y));
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    swap(_Rb_tree& __t)
	    _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Compare>::value)
	    {
	      if (_M_root() == 0)
		{
		  if (__t._M_root() != 0)
		    _M_impl._M_move_data(__t._M_impl);
		}
	      else if (__t._M_root() == 0)
		__t._M_impl._M_move_data(_M_impl);
	      else
		{
		  std::swap(_M_root(),__t._M_root());
		  std::swap(_M_leftmost(),__t._M_leftmost());
		  std::swap(_M_rightmost(),__t._M_rightmost());
		  
		  _M_root()->_M_parent = _M_end();
		  __t._M_root()->_M_parent = __t._M_end();
		  std::swap(this->_M_impl._M_node_count, __t._M_impl._M_node_count);
		}
	      // No need to swap header's color as it does not change.
	      std::swap(this->_M_impl._M_key_compare, __t._M_impl._M_key_compare);
	
	      _Alloc_traits::_S_on_swap(_M_get_Node_allocator(),
					__t._M_get_Node_allocator());
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr,
		 typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_get_insert_unique_pos(const key_type& __k)
	    {
	      typedef pair<_Base_ptr, _Base_ptr> _Res;
	      _Link_type __x = _M_begin();
	      _Base_ptr __y = _M_end();
	      bool __comp = true;
	      while (__x != 0)
		{
		  __y = __x;
		  __comp = _M_impl._M_key_compare(__k, _S_key(__x));
		  __x = __comp ? _S_left(__x) : _S_right(__x);
		}
	      iterator __j = iterator(__y);
	      if (__comp)
		{
		  if (__j == begin())
		    return _Res(__x, __y);
		  else
		    --__j;
		}
	      if (_M_impl._M_key_compare(_S_key(__j._M_node), __k))
		return _Res(__x, __y);
	      return _Res(__j._M_node, 0);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr,
		 typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_get_insert_equal_pos(const key_type& __k)
	    {
	      typedef pair<_Base_ptr, _Base_ptr> _Res;
	      _Link_type __x = _M_begin();
	      _Base_ptr __y = _M_end();
	      while (__x != 0)
		{
		  __y = __x;
		  __x = _M_impl._M_key_compare(__k, _S_key(__x)) ?
		        _S_left(__x) : _S_right(__x);
		}
	      return _Res(__x, __y);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg>
	#endif
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::iterator, bool>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	#if __cplusplus >= 201103L
	    _M_insert_unique(_Arg&& __v)
	#else
	    _M_insert_unique(const _Val& __v)
	#endif
	    {
	      typedef pair<iterator, bool> _Res;
	      pair<_Base_ptr, _Base_ptr> __res
		= _M_get_insert_unique_pos(_KeyOfValue()(__v));
	
	      if (__res.second)
		{
		  _Alloc_node __an(*this);
		  return _Res(_M_insert_(__res.first, __res.second,
					 _GLIBCXX_FORWARD(_Arg, __v), __an),
			      true);
		}
	
	      return _Res(iterator(__res.first), false);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg>
	#endif
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	#if __cplusplus >= 201103L
	    _M_insert_equal(_Arg&& __v)
	#else
	    _M_insert_equal(const _Val& __v)
	#endif
	    {
	      pair<_Base_ptr, _Base_ptr> __res
		= _M_get_insert_equal_pos(_KeyOfValue()(__v));
	      _Alloc_node __an(*this);
	      return _M_insert_(__res.first, __res.second,
				_GLIBCXX_FORWARD(_Arg, __v), __an);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr,
	         typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_get_insert_hint_unique_pos(const_iterator __position,
					  const key_type& __k)
	    {
	      iterator __pos = __position._M_const_cast();
	      typedef pair<_Base_ptr, _Base_ptr> _Res;
	
	      // end()
	      if (__pos._M_node == _M_end())
		{
		  if (size() > 0
		      && _M_impl._M_key_compare(_S_key(_M_rightmost()), __k))
		    return _Res(0, _M_rightmost());
		  else
		    return _M_get_insert_unique_pos(__k);
		}
	      else if (_M_impl._M_key_compare(__k, _S_key(__pos._M_node)))
		{
		  // First, try before...
		  iterator __before = __pos;
		  if (__pos._M_node == _M_leftmost()) // begin()
		    return _Res(_M_leftmost(), _M_leftmost());
		  else if (_M_impl._M_key_compare(_S_key((--__before)._M_node), __k))
		    {
		      if (_S_right(__before._M_node) == 0)
			return _Res(0, __before._M_node);
		      else
			return _Res(__pos._M_node, __pos._M_node);
		    }
		  else
		    return _M_get_insert_unique_pos(__k);
		}
	      else if (_M_impl._M_key_compare(_S_key(__pos._M_node), __k))
		{
		  // ... then try after.
		  iterator __after = __pos;
		  if (__pos._M_node == _M_rightmost())
		    return _Res(0, _M_rightmost());
		  else if (_M_impl._M_key_compare(__k, _S_key((++__after)._M_node)))
		    {
		      if (_S_right(__pos._M_node) == 0)
			return _Res(0, __pos._M_node);
		      else
			return _Res(__after._M_node, __after._M_node);
		    }
		  else
		    return _M_get_insert_unique_pos(__k);
		}
	      else
		// Equivalent keys.
		return _Res(__pos._M_node, 0);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg, typename _NodeGen>
	#else
	    template<typename _NodeGen>
	#endif
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_insert_unique_(const_iterator __position,
	#if __cplusplus >= 201103L
				_Arg&& __v,
	#else
				const _Val& __v,
	#endif
				_NodeGen& __node_gen)
	    {
	      pair<_Base_ptr, _Base_ptr> __res
		= _M_get_insert_hint_unique_pos(__position, _KeyOfValue()(__v));
	
	      if (__res.second)
		return _M_insert_(__res.first, __res.second,
				  _GLIBCXX_FORWARD(_Arg, __v),
				  __node_gen);
	      return iterator(__res.first);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr,
	         typename _Rb_tree<_Key, _Val, _KeyOfValue,
				   _Compare, _Alloc>::_Base_ptr>
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_get_insert_hint_equal_pos(const_iterator __position, const key_type& __k)
	    {
	      iterator __pos = __position._M_const_cast();
	      typedef pair<_Base_ptr, _Base_ptr> _Res;
	
	      // end()
	      if (__pos._M_node == _M_end())
		{
		  if (size() > 0
		      && !_M_impl._M_key_compare(__k, _S_key(_M_rightmost())))
		    return _Res(0, _M_rightmost());
		  else
		    return _M_get_insert_equal_pos(__k);
		}
	      else if (!_M_impl._M_key_compare(_S_key(__pos._M_node), __k))
		{
		  // First, try before...
		  iterator __before = __pos;
		  if (__pos._M_node == _M_leftmost()) // begin()
		    return _Res(_M_leftmost(), _M_leftmost());
		  else if (!_M_impl._M_key_compare(__k, _S_key((--__before)._M_node)))
		    {
		      if (_S_right(__before._M_node) == 0)
			return _Res(0, __before._M_node);
		      else
			return _Res(__pos._M_node, __pos._M_node);
		    }
		  else
		    return _M_get_insert_equal_pos(__k);
		}
	      else
		{
		  // ... then try after.  
		  iterator __after = __pos;
		  if (__pos._M_node == _M_rightmost())
		    return _Res(0, _M_rightmost());
		  else if (!_M_impl._M_key_compare(_S_key((++__after)._M_node), __k))
		    {
		      if (_S_right(__pos._M_node) == 0)
			return _Res(0, __pos._M_node);
		      else
			return _Res(__after._M_node, __after._M_node);
		    }
		  else
		    return _Res(0, 0);
		}
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	#if __cplusplus >= 201103L
	    template<typename _Arg, typename _NodeGen>
	#else
	    template<typename _NodeGen>
	#endif
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_insert_equal_(const_iterator __position,
	#if __cplusplus >= 201103L
			       _Arg&& __v,
	#else
			       const _Val& __v,
	#endif
			       _NodeGen& __node_gen)
	      {
		pair<_Base_ptr, _Base_ptr> __res
		  = _M_get_insert_hint_equal_pos(__position, _KeyOfValue()(__v));
	
		if (__res.second)
		  return _M_insert_(__res.first, __res.second,
				    _GLIBCXX_FORWARD(_Arg, __v),
				    __node_gen);
	
		return _M_insert_equal_lower(_GLIBCXX_FORWARD(_Arg, __v));
	      }
	
	#if __cplusplus >= 201103L
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_insert_node(_Base_ptr __x, _Base_ptr __p, _Link_type __z)
	    {
	      bool __insert_left = (__x != 0 || __p == _M_end()
				    || _M_impl._M_key_compare(_S_key(__z),
							      _S_key(__p)));
	
	      _Rb_tree_insert_and_rebalance(__insert_left, __z, __p,
					    this->_M_impl._M_header);
	      ++_M_impl._M_node_count;
	      return iterator(__z);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_insert_lower_node(_Base_ptr __p, _Link_type __z)
	    {
	      bool __insert_left = (__p == _M_end()
				    || !_M_impl._M_key_compare(_S_key(__p),
							       _S_key(__z)));
	
	      _Rb_tree_insert_and_rebalance(__insert_left, __z, __p,
					    this->_M_impl._M_header);
	      ++_M_impl._M_node_count;
	      return iterator(__z);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_insert_equal_lower_node(_Link_type __z)
	    {
	      _Link_type __x = _M_begin();
	      _Base_ptr __y = _M_end();
	      while (__x != 0)
		{
		  __y = __x;
		  __x = !_M_impl._M_key_compare(_S_key(__x), _S_key(__z)) ?
		        _S_left(__x) : _S_right(__x);
		}
	      return _M_insert_lower_node(__y, __z);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename... _Args>
	      pair<typename _Rb_tree<_Key, _Val, _KeyOfValue,
				     _Compare, _Alloc>::iterator, bool>
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_emplace_unique(_Args&&... __args)
	      {
		_Link_type __z = _M_create_node(std::forward<_Args>(__args)...);
	
		__try
		  {
		    typedef pair<iterator, bool> _Res;
		    auto __res = _M_get_insert_unique_pos(_S_key(__z));
		    if (__res.second)
		      return _Res(_M_insert_node(__res.first, __res.second, __z), true);
		
		    _M_drop_node(__z);
		    return _Res(iterator(__res.first), false);
		  }
		__catch(...)
		  {
		    _M_drop_node(__z);
		    __throw_exception_again;
		  }
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename... _Args>
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_emplace_equal(_Args&&... __args)
	      {
		_Link_type __z = _M_create_node(std::forward<_Args>(__args)...);
	
		__try
		  {
		    auto __res = _M_get_insert_equal_pos(_S_key(__z));
		    return _M_insert_node(__res.first, __res.second, __z);
		  }
		__catch(...)
		  {
		    _M_drop_node(__z);
		    __throw_exception_again;
		  }
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename... _Args>
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_emplace_hint_unique(const_iterator __pos, _Args&&... __args)
	      {
		_Link_type __z = _M_create_node(std::forward<_Args>(__args)...);
	
		__try
		  {
		    auto __res = _M_get_insert_hint_unique_pos(__pos, _S_key(__z));
	
		    if (__res.second)
		      return _M_insert_node(__res.first, __res.second, __z);
	
		    _M_drop_node(__z);
		    return iterator(__res.first);
		  }
		__catch(...)
		  {
		    _M_drop_node(__z);
		    __throw_exception_again;
		  }
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    template<typename... _Args>
	      typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator
	      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	      _M_emplace_hint_equal(const_iterator __pos, _Args&&... __args)
	      {
		_Link_type __z = _M_create_node(std::forward<_Args>(__args)...);
	
		__try
		  {
		    auto __res = _M_get_insert_hint_equal_pos(__pos, _S_key(__z));
	
		    if (__res.second)
		      return _M_insert_node(__res.first, __res.second, __z);
	
		    return _M_insert_equal_lower_node(__z);
		  }
		__catch(...)
		  {
		    _M_drop_node(__z);
		    __throw_exception_again;
		  }
	      }
	#endif
	
	  template<typename _Key, typename _Val, typename _KoV,
	           typename _Cmp, typename _Alloc>
	    template<class _II>
	      void
	      _Rb_tree<_Key, _Val, _KoV, _Cmp, _Alloc>::
	      _M_insert_unique(_II __first, _II __last)
	      {
		_Alloc_node __an(*this);
		for (; __first != __last; ++__first)
		  _M_insert_unique_(end(), *__first, __an);
	      }
	
	  template<typename _Key, typename _Val, typename _KoV,
	           typename _Cmp, typename _Alloc>
	    template<class _II>
	      void
	      _Rb_tree<_Key, _Val, _KoV, _Cmp, _Alloc>::
	      _M_insert_equal(_II __first, _II __last)
	      {
		_Alloc_node __an(*this);
		for (; __first != __last; ++__first)
		  _M_insert_equal_(end(), *__first, __an);
	      }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_erase_aux(const_iterator __position)
	    {
	      _Link_type __y =
		static_cast<_Link_type>(_Rb_tree_rebalance_for_erase
					(const_cast<_Base_ptr>(__position._M_node),
					 this->_M_impl._M_header));
	      _M_drop_node(__y);
	      --_M_impl._M_node_count;
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    _M_erase_aux(const_iterator __first, const_iterator __last)
	    {
	      if (__first == begin() && __last == end())
		clear();
	      else
		while (__first != __last)
		  _M_erase_aux(__first++);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::size_type
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    erase(const _Key& __x)
	    {
	      pair<iterator, iterator> __p = equal_range(__x);
	      const size_type __old_size = size();
	      _M_erase_aux(__p.first, __p.second);
	      return __old_size - size();
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    void
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    erase(const _Key* __first, const _Key* __last)
	    {
	      while (__first != __last)
		erase(*__first++);
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    find(const _Key& __k)
	    {
	      iterator __j = _M_lower_bound(_M_begin(), _M_end(), __k);
	      return (__j == end()
		      || _M_impl._M_key_compare(__k,
						_S_key(__j._M_node))) ? end() : __j;
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue,
			      _Compare, _Alloc>::const_iterator
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    find(const _Key& __k) const
	    {
	      const_iterator __j = _M_lower_bound(_M_begin(), _M_end(), __k);
	      return (__j == end()
		      || _M_impl._M_key_compare(__k, 
						_S_key(__j._M_node))) ? end() : __j;
	    }
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    typename _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::size_type
	    _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
	    count(const _Key& __k) const
	    {
	      pair<const_iterator, const_iterator> __p = equal_range(__k);
	      const size_type __n = std::distance(__p.first, __p.second);
	      return __n;
	    }
	
	  _GLIBCXX_PURE unsigned int
	  _Rb_tree_black_count(const _Rb_tree_node_base* __node,
	                       const _Rb_tree_node_base* __root) throw ();
	
	  template<typename _Key, typename _Val, typename _KeyOfValue,
	           typename _Compare, typename _Alloc>
	    bool
	    _Rb_tree<_Key,_Val,_KeyOfValue,_Compare,_Alloc>::__rb_verify() const
	    {
	      if (_M_impl._M_node_count == 0 || begin() == end())
		return _M_impl._M_node_count == 0 && begin() == end()
		       && this->_M_impl._M_header._M_left == _M_end()
		       && this->_M_impl._M_header._M_right == _M_end();
	
	      unsigned int __len = _Rb_tree_black_count(_M_leftmost(), _M_root());
	      for (const_iterator __it = begin(); __it != end(); ++__it)
		{
		  _Const_Link_type __x = static_cast<_Const_Link_type>(__it._M_node);
		  _Const_Link_type __L = _S_left(__x);
		  _Const_Link_type __R = _S_right(__x);
	
		  if (__x->_M_color == _S_red)
		    if ((__L && __L->_M_color == _S_red)
			|| (__R && __R->_M_color == _S_red))
		      return false;
	
		  if (__L && _M_impl._M_key_compare(_S_key(__x), _S_key(__L)))
		    return false;
		  if (__R && _M_impl._M_key_compare(_S_key(__R), _S_key(__x)))
		    return false;
	
		  if (!__L && !__R && _Rb_tree_black_count(__x, _M_root()) != __len)
		    return false;
		}
	
	      if (_M_leftmost() != _Rb_tree_node_base::_S_minimum(_M_root()))
		return false;
	      if (_M_rightmost() != _Rb_tree_node_base::_S_maximum(_M_root()))
		return false;
	      return true;
	    }
	
	#if __cplusplus > 201402L
	  // Allow access to internals of compatible _Rb_tree specializations.
	  template<typename _Key, typename _Val, typename _Sel, typename _Cmp1,
		   typename _Alloc, typename _Cmp2>
	    struct _Rb_tree_merge_helper<_Rb_tree<_Key, _Val, _Sel, _Cmp1, _Alloc>,
					 _Cmp2>
	    {
	    private:
	      friend class _Rb_tree<_Key, _Val, _Sel, _Cmp1, _Alloc>;
	
	      static auto&
	      _S_get_impl(_Rb_tree<_Key, _Val, _Sel, _Cmp2, _Alloc>& __tree)
	      { return __tree._M_impl; }
	    };
	#endif // C++17
	
	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace
	
	#endif