fancy_pair.h

template <typename T, typename U>
struct pair {
    T first;
    U second;

    constexpr std::strong_ordering operator<=>(const pair& other) const {
        if (auto first_comp = first <=> other.first; first_comp != 0) {
            return first_comp;
        } else {
            return second <=> other.second;
        }
    }
};