#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

#include <atcoder/math>

int main() {
    int T;
    cin >> T;

    while (T--) {
        ll N, M;
        cin >> N >> M;

        ll mod = 1e9;
        N %= mod, M %= mod, M = (mod - M) % mod;

        if (M == N) {
            cout << 1 << '\n';
        } else if (N == 0) {
            cout << -1 << '\n';
        } else if (M == 0) {
            cout << mod << '\n';
        } else {
            auto [res, lcm] = atcoder::crt({0, M}, {N, mod});

            if (lcm == 0 || res % N != 0) {
                cout << -1 << '\n';
            } else {
                cout << res / N << '\n';
            }
        }
    }
}