namespace std { template <class T1, class T2> struct pair { using first_type = T1; using second_type = T2; T1 first; T2 second; pair(const pair&) = default; pair(pair&&) = default; EXPLICIT constexpr pair(); EXPLICIT constexpr pair(const T1& x, const T2& y); template<class U1, class U2> EXPLICIT constexpr pair(U1&& x, U2&& y); template<class U1, class U2> EXPLICIT constexpr pair(const pair<U1, U2>& p); template<class U1, class U2> EXPLICIT constexpr pair(pair<U1, U2>&& p); template <class... Args1, class... Args2> pair(piecewise_construct_t, tuple<Args1...> first_args, tuple<Args2...> second_args); pair& operator=(const pair& p); template<class U1, class U2> pair& operator=(const pair<U1, U2>& p); pair& operator=(pair&& p) noexcept(see below); template<class U1, class U2> pair& operator=(pair<U1, U2>&& p); void swap(pair& p) noexcept(see below); }; template<class T1, class T2> pair(T1, T2) -> pair<T1, T2>; }
EXPLICIT constexpr pair();
EXPLICIT constexpr pair(const T1& x, const T2& y);
template<class U1, class U2> EXPLICIT constexpr pair(U1&& x, U2&& y);
template<class U1, class U2> EXPLICIT constexpr pair(const pair<U1, U2>& p);
template<class U1, class U2> EXPLICIT constexpr pair(pair<U1, U2>&& p);
template<class... Args1, class... Args2>
pair(piecewise_construct_t, tuple<Args1...> first_args, tuple<Args2...> second_args);
pair& operator=(const pair& p);
template<class U1, class U2> pair& operator=(const pair<U1, U2>& p);
pair& operator=(pair&& p) noexcept(see below);
is_nothrow_move_assignable_v<T1> && is_nothrow_move_assignable_v<T2>
template<class U1, class U2> pair& operator=(pair<U1, U2>&& p);
void swap(pair& p) noexcept(see below);
template <class T1, class T2>
constexpr bool operator==(const pair<T1, T2>& x, const pair<T1, T2>& y);
template <class T1, class T2>
constexpr bool operator<(const pair<T1, T2>& x, const pair<T1, T2>& y);
template <class T1, class T2>
constexpr bool operator!=(const pair<T1, T2>& x, const pair<T1, T2>& y);
template <class T1, class T2>
constexpr bool operator>(const pair<T1, T2>& x, const pair<T1, T2>& y);
template <class T1, class T2>
constexpr bool operator>=(const pair<T1, T2>& x, const pair<T1, T2>& y);
template <class T1, class T2>
constexpr bool operator<=(const pair<T1, T2>& x, const pair<T1, T2>& y);
template<class T1, class T2> void swap(pair<T1, T2>& x, pair<T1, T2>& y)
noexcept(noexcept(x.swap(y)));
template <class T1, class T2>
constexpr pair<V1, V2> make_pair(T1&& x, T2&& y);
template <class T1, class T2>
struct tuple_size<pair<T1, T2>> : integral_constant<size_t, 2> { };
tuple_element<0, pair<T1, T2>>::type
tuple_element<1, pair<T1, T2>>::type
template<size_t I, class T1, class T2>
constexpr tuple_element_t<I, pair<T1, T2>>& get(pair<T1, T2>& p) noexcept;
template<size_t I, class T1, class T2>
constexpr const tuple_element_t<I, pair<T1, T2>>& get(const pair<T1, T2>& p) noexcept;
template<size_t I, class T1, class T2>
constexpr tuple_element_t<I, pair<T1, T2>>&& get(pair<T1, T2>&& p) noexcept;
template<size_t I, class T1, class T2>
constexpr const tuple_element_t<I, pair<T1, T2>>&& get(const pair<T1, T2>&& p) noexcept;
template <class T1, class T2>
constexpr T1& get(pair<T1, T2>& p) noexcept;
template <class T1, class T2>
constexpr const T1& get(const pair<T1, T2>& p) noexcept;
template <class T1, class T2>
constexpr T1&& get(pair<T1, T2>&& p) noexcept;
template <class T1, class T2>
constexpr const T1&& get(const pair<T1, T2>&& p) noexcept;
template <class T2, class T1>
constexpr T2& get(pair<T1, T2>& p) noexcept;
template <class T2, class T1>
constexpr const T2& get(const pair<T1, T2>& p) noexcept;
template <class T2, class T1>
constexpr T2&& get(pair<T1, T2>&& p) noexcept;
template <class T2, class T1>
constexpr const T2&& get(const pair<T1, T2>&& p) noexcept;
struct piecewise_construct_t {
explicit piecewise_construct_t() = default;
};
inline constexpr piecewise_construct_t piecewise_construct{};