#include <bits/stdc++.h>

using namespace std;


int main(){
    int q;
    cin >> q;
    for(int a0 = 0; a0 < q; a0++){
        int len;
        int c;
        cin >> len >> c;
        // your code goes here
        int limit = ((len - 1) * (len -2)) / 2;
        if (c > limit) {
            cout << -1 << endl;
            break;
        }
            
    }
    return 0;
}