#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int M = 31623;

void solve(){
    ll A, B, mi=2e9;
    cin >> A >> B;

    for (int X=0; X<=M; X++){
        if ((B+X) % (A+X) == 0){
            mi = X;
            break;
        }
    }

    for (int Y=2; Y<=M; Y++){
        if (B-A*Y >= 0 && (B-A*Y) % (Y-1) == 0) mi = min(mi, (B-A*Y) / (Y-1));
    }

    if (mi == 2e9) cout << -1 << '\n';
    else cout << mi << '\n';
}

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    int T;
    cin >> T;

    while(T--) solve();

    return 0;
}