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

tuple<ll, ll, ll> extGCD(ll a, ll b) {
    if (b == 0) return make_tuple(a, 1, 0);
    ll q = a / b, r = a % b;
    auto [g, s, t] = extGCD(b, r);
    ll x = t;
    ll y = s - q * t;
    return make_tuple(g, x, y);
}

ll modInvGcd(ll a, ll mod) {
    auto [g, x, y] = extGCD(a, mod);
    if (g != 1) return -1;
    return x % mod;
}

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

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

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

        if (M == N) {
            cout << 1 << '\n';
        } else if (gcd(mod, N) == 1) {
            ll invN = (mod + modInvGcd(N, mod)) % mod;
            cout << (M * invN) % mod << '\n';
        } else if (N != 0 && M % N == 0) {
            cout << M / N << '\n';
        } else {
            cout << -1 << '\n';
        }
    }
}