#include <bits/stdc++.h>
#include <atcoder/all>
// using mint = atcoder::static_modint<998244353>;
// //using mint = atcoder::static_modint<1000000007>;
using namespace std;
using namespace atcoder;
using ld = long double;
using ll = long long;
#define mp(a,b) make_pair(a,b)
#define rep(i,s,n) for(int i=s; i<(int)n; i++)
const vector<int> dx{1,0,-1,0},dy{0,1,0,-1};


void solve(){
    ll mod=1e9;
    ll n,m;cin >> n >> m;
    n%=mod;
    m=(mod-m%mod)%mod;
    if(n==0){
        if(m==0)cout << 1 << "\n";
        else cout << -1 << "\n";
        return;
    }
    ll ord=mod*100;
    while(n%2==0){
        n/=2;
        mod/=2;
        if(m%2!=0){
            cout << -1 << "\n";
            return;
        }
        m/=2;
    }
    while(n%5==0){
        n/=5;
        mod/=5;
        if(m%5!=0){
            cout << -1 << "\n";
            return;
        }
        m/=5;
    }
    ll inv_n=pow_mod(n,ord-1,mod);
    ll ans=m*inv_n%mod;
    if(ans==0)ans+=mod;
    cout << ans << "\n";

}
int main(){
    int T;cin >> T;
    rep(i,0,T)solve();
}