#include <initializer_list>

namespace std {
  // クラステンプレート unordered_set
  template <class Key,
            class Hash = std::hash<Key>,
            class Pred = std::equal_to<Key>,
            class Allocator = std::allocator<Key> >
    class unordered_set;

  // クラステンプレート unordered_multiset
  template <class Key,
            class Hash = std::hash<Key>,
            class Pred = std::equal_to<Key>,
            class Allocator = std::allocator<Key> >
    class unordered_multiset;

  template <class Key, class Hash, class Pred, class Allocator>
    void swap(unordered_set<Key, Hash, Pred, Allocator>& x,
              unordered_set<Key, Hash, Pred, Allocator>& y);

  template <class Key, class Hash, class Pred, class Allocator>
    void swap(unordered_multiset<Key, Hash, Pred, Allocator>& x,
              unordered_multiset<Key, Hash, Pred, Allocator>& y);

  template <class Key, class Hash, class Pred, class Allocator>
    bool operator==(const unordered_set<Key, Hash, Pred, Allocator>& a,
                    const unordered_set<Key, Hash, Pred, Allocator>& b);
  template <class Key, class Hash, class Pred, class Allocator>
    bool operator!=(const unordered_set<Key, Hash, Pred, Allocator>& a,
                    const unordered_set<Key, Hash, Pred, Allocator>& b);

  template <class Key, class Hash, class Pred, class Allocator>
    bool operator==(const unordered_multiset<Key, Hash, Pred, Allocator>& a,
                    const unordered_multiset<Key, Hash, Pred, Allocator>& b);
  template <class Key, class Hash, class Pred, class Allocator>
    bool operator!=(const unordered_multiset<Key, Hash, Pred, Allocator>& a,
                    const unordered_multiset<Key, Hash, Pred, Allocator>& b);
}