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

long long gcd(long long a, long long b){
    if (b == 0) return a;
    return gcd(b, a%b);
}

int main() {
    long long N, M;
    cin >> N >> M;
    long long g = gcd(N, M);
    N /= g;
    M /= g;
    while (N % 10 == 0) N /= 10;
    N %= 10;
    while (M % 5 == 0){
        M /= 5;
        N *= 2;
        while(N%10==0)N %= 10;
    }
    while (M % 2 == 0){
        M /= 2;
        N *= 5;
        while(N%10==0)N %= 10;
    }
    if (M == 1) cout << N << endl;
    else cout << -1 << endl;
}