#include <cassert>
#include <map>
#include <utility>
struct Comp {
using is_transparent = void;
bool operator()(const std::pair<int, int> &lhs,
const std::pair<int, int> &rhs) const {
return lhs < rhs;
}
bool operator()(const std::pair<int, int> &lhs, int rhs) const {
return lhs.first < rhs;
}
bool operator()(int lhs, const std::pair<int, int> &rhs) const {
return lhs < rhs.first;
}
};
int main(int, char**) {
std::map<std::pair<int, int>, int, Comp> s{
{{2, 1}, 1}, {{1, 2}, 2}, {{1, 3}, 3}, {{1, 4}, 4}, {{2, 2}, 5}};
auto cnt = s.count(1);
assert(cnt == 3);
return 0;
}