pair compare

#include <algorithm>
#include <iostream>
#include <vector>

bool compare(std::pair<size_t, size_t> const &first,
             std::pair<size_t, size_t> const &second) {
    if (first.second == second.second) {
        return first.first < second.first;
    }
    return first.second < second.second;
}

int main() {
    size_t n;
    std::cin >> n;

    std::vector<std::pair<size_t, size_t>> arr(n);
    for (auto &pair : arr) {
        std::cin >> pair.first >> pair.second;
    }

    std::sort(arr.begin(), arr.end(), compare);

    for (auto const &pair : arr) {
        std::cout << pair.first << ' ' << pair.second << '\n';
    }

    return 0;
}