template<class RandomAccessIterator>
constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last);
template<class ExecutionPolicy, class RandomAccessIterator>
void nth_element(ExecutionPolicy&& exec,
RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last);
template<class RandomAccessIterator, class Compare>
constexpr void nth_element(RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last, Compare comp);
template<class ExecutionPolicy, class RandomAccessIterator, class Compare>
void nth_element(ExecutionPolicy&& exec,
RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last, Compare comp);
template<random_access_iterator I, sentinel_for<I> S, class Comp = ranges::less,
class Proj = identity>
requires sortable<I, Comp, Proj>
constexpr I
ranges::nth_element(I first, I nth, S last, Comp comp = {}, Proj proj = {});
template<random_access_range R, class Comp = ranges::less, class Proj = identity>
requires sortable<iterator_t<R>, Comp, Proj>
constexpr borrowed_iterator_t<R>
ranges::nth_element(R&& r, iterator_t<R> nth, Comp comp = {}, Proj proj = {});