#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;

void solve(){
    ll n, m;
    cin >> n >> m;
    auto pa = atcoder::crt({-m, 0}, {1'000'000'000, n});
    if(pa.second == 0){
        cout << "-1\n";
        return;
    }
    cout << pa.first / n << '\n';
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T;
    cin >> T;
    while(T--) solve();
}