#include <bits/stdc++.h>
using namespace std;

long long eazymod(long long a,long long m){a %= m; if(a < 0) a += m; return a;}
pair<long long,long long> invgcd(long long a,long long b){
    //return {gcd(a,b),x} (xa≡g(mod b))
    a = eazymod(a,b);
    if(a == 0) return {b,0};
    long long x = 0,y = 1,memob = b;
    while(a){
        long long q = b/a;
        b -= a*q;
        swap(x,y); y -= q*x;
        swap(a,b);
    }
    if(x < 0) x += memob/b;
    return {b,x};
}
 
pair<long long,long long> CRT(vector<long long> A,vector<long long> M){
    int n = A.size(); //0 <= Ai < Mi,|A| = |M|
    long long x = 0,lcm = 1;
    for(int i=0; i<n; i++){
        long long a = A.at(i)%M.at(i),m = M.at(i);
        if(lcm < m) swap(lcm,m),swap(x,a);
        if(lcm%m == 0){
            if(x%m != a) return {-1,-1};
            continue;
        }
        auto[g,in] = invgcd(lcm,m);
        if((a-x)%g) return {-1,-1};
 
        long long u1 = m/g;
        long long y = (a-x)/g %u1 * in %u1;
        x += y*lcm; lcm *= u1;
        if(x < 0) x += lcm;
    }
    return {x,lcm};
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int T; cin >> T;
    long long Mod = 1'000'000'000;
    while(T--){
        long long N,M; cin >> N >> M;
        N %= Mod; M %= Mod;
        if(N == 0){
            if(M == 0) cout << 1 << "\n";
            else cout << "-1\n";
            continue;
        }
        long long g = gcd(Mod,N);
        if(M%g){cout << "-1\n"; continue;}
        if(M == 0){cout << Mod/g << "\n"; continue;}
        int time2 = 9,time5 = 9;
        while(g%2 == 0) time2--,g /= 2,N /= 2,M /= 2;
        while(g%5 == 0) time5--,g /= 5,N /= 5,M /= 5;

        long long two = 0,five = 0,mod2 = 1,mod5 = 1;
        {
            vector<long long> OK = {0,1};
            for(int i=0; i<time2; i++){
                mod2 *= 2;
                long long n = N%mod2,m = M%mod2;
                for(int k=0; k<2; k++){
                    long long v = OK.at(k);
                    if((n*v+m)%mod2 == 0){
                        OK.clear();
                        for(int l=0; l<2; l++) OK.push_back(v+mod2*l);
                        break;
                    }
                }
            }
            two = OK.at(0);
        }
        {
            vector<long long> OK = {0,1,2,3,4};
            for(int i=0; i<time5; i++){
                mod5 *= 5;
                long long n = N%mod5,m = M%mod5;
                for(int k=0; k<5; k++){
                    long long v = OK.at(k);
                    if((n*v+m)%mod5 == 0){
                        OK.clear();
                        for(int l=0; l<5; l++) OK.push_back(v+mod5*l);
                        break;
                    }
                }
            }
            five = OK.at(0);
        }
        auto [ans,ign] = CRT({two,five},{mod2,mod5});
        cout << ans << "\n";
    }
}