#include <iostream>
#include <string>
#include <set>
#include <tuple>
using namespace std;
 
int main() {
    auto lexical_compare = [](tuple<int, int> a, tuple<int, int> b) { return get<0>(a) == get<0>(b); };
    set<tuple<int, int>, decltype(lexical_compare)> s(lexical_compare);
 
    s.insert({1,2});
    s.insert({1,3});
    s.insert({2,1});
    s.insert({2,2});
    s.insert({2,3});
    s.insert({1,1});
 
    for (auto[x, y] : s)
        cout << x << ' ' << y << endl;
 
    return 0;
}

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