//I_F_A
#include "bits/stdc++.h"
using namespace std;
int main(){
    
    long int tc;
    cin >> tc;
    
    while(tc--){
        
        long long n,k;
        cin >> n >> k;
        
        if(k > (n*(n-1))/2)
            cout << -1 << endl;
    }
}