#include <compare>
#include <initializer_list>
namespace std {
template<class Key, class Compare = less<Key>, class KeyContainer = vector<Key>>
class flat_set;
struct sorted_unique_t { explicit sorted_unique_t() = default; };
inline constexpr sorted_unique_t sorted_unique{};
template<class Key, class Compare, class KeyContainer, class Allocator>
struct uses_allocator<flat_set<Key, Compare, KeyContainer>, Allocator>;
template<class Key, class Compare, class KeyContainer, class Predicate>
typename flat_set<Key, Compare, KeyContainer>::size_type
erase_if(flat_set<Key, Compare, KeyContainer>& c, Predicate pred);
template<class Key, class Compare = less<Key>, class KeyContainer = vector<Key>>
class flat_multiset;
struct sorted_equivalent_t { explicit sorted_equivalent_t() = default; };
inline constexpr sorted_equivalent_t sorted_equivalent{};
template<class Key, class Compare, class KeyContainer, class Allocator>
struct uses_allocator<flat_multiset<Key, Compare, KeyContainer>, Allocator>;
template<class Key, class Compare, class KeyContainer, class Predicate>
typename flat_multiset<Key, Compare, KeyContainer>::size_type
erase_if(flat_multiset<Key, Compare, KeyContainer>& c, Predicate pred);
}