Timus: 1178 - Akbardin's Roads

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

using namespace std;

int main()
{
    int n;
    cin >> n;
    vector <pair<pair<int, int>, int> > v(n);
    for(int i=0; i<n; i++)
    {
        v[i].second = i;
        cin >> v[i].first.first >> v[i].first.second;
    }
    sort(v.begin(), v.end());

    for(int i=0; i<n; i+=2)
    {
        cout << v[i].second+1 << " " << v[i+1].second+1 << endl;
    }

    return 0;
}