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

// extGCD(a,b) -> {g,x,y} : g=gcd(a,b), ax+by=g
tuple<ll, ll, ll> extGCD(ll a, ll b) {
    if (b == 0) return {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 {g, x, y};
}

// a の mod 逆元を求める
// ax=1(mod m) <-> ax+my=1(mod m)
// gcd(a,m)=1 でない場合、-1 を返す。
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;

        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 {
            ll G = gcd(gcd(N, M), mod);
            N /= G, M /= G, mod /= G;

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

                ll ans = M * invN;
                cout << ans % mod << '\n';
            }
        }
    }
}