USACO-T022: Ordered Fractions

/*
ID: mickyta1
TASK: frac1
LANG: C++
*/

#include <bits/stdc++.h>
using namespace std;

#define f first
#define s second
typedef pair<int, int> pii;

bool comp(const pii &lhs, const pii &rhs){
    int l = lhs.f * rhs.s;
    int r = rhs.f * lhs.s;
    return l < r;
}

set<pii, decltype(&comp)> stt(comp);

int main(){
    freopen("frac1.in", "r", stdin);
    freopen("frac1.out", "w", stdout);

    int n;
    scanf("%d", &n);
    stt.emplace(0, 1);
    stt.emplace(1, 1);
    for(int i = 1; i <= n - 1; ++i){
        for(int j = i + 1; j <= n; ++j){
            stt.emplace(i, j);
        }
    }
    for(pii p : stt){
        cout << p.f << '/' << p.s << '\n';
    }

    fclose(stdin);
    fclose(stdout);
    return 0;
}