#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define lll __int128
const ll mod = 1e9;

lll ex_gcd(lll a,lll b,lll &x,lll &y) {
    if(!b) {x=1; y=0; return a;}
    lll d=ex_gcd(b,a%b,y,x);
    y-=a/b*x; return d;
}
inline lll inv(lll a,lll m) {
    lll x,y,d;
    d=ex_gcd(a,m,x,y);
    return (x+m)%m;
}
inline lll cal(lll a, lll b, lll c) {
    lll x, y;
    lll d = ex_gcd(a, b, x, y);
    if (c % d != 0)
        return -1;
    x *= c / d;
    b /= d;
    if (b < 0) b = -b;
    lll ans = x % b;
    while (ans <= 0) //最小正整数解
        ans += b;
    return ans;
}

inline void Solve() {
    ll n, m;
    cin >> n >> m;
    ll m0 = (mod - m % mod) % mod;
    ll d = __gcd(n, mod);
    if (m0 % d == 0) {
        printf("%lld\n", (ll)cal(n,  mod, m0));
    } else {
        printf("-1\n");
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int T;
    cin >> T;
    for (;T--;)
        Solve();
    return 0;
}