#include <bits/stdc++.h>
using namespace std;
long long gcd(long long A, long long B){
  if (B == 0){
    return A;
  } else {
    return gcd(B, A % B);
  }
}
int main(){
  long long N, M;
  cin >> N >> M;
  long long g = gcd(N, M);
  N /= g;
  M /= g;
  long long M2 = M;
  int cnt2 = 0;
  while (M2 % 2 == 0){
    M2 /= 2;
    cnt2++;
  }
  int cnt5 = 0;
  while (M2 % 5 == 0){
    M2 /= 5;
    cnt5++;
  }
  if (M2 != 1){
    cout << -1 << endl;
  } else {
    while (N % 10 == 0){
      N /= 10;
    }
    N %= 10;
    if (cnt2 > cnt5){
      for (int i = 0; i < cnt2 - cnt5; i++){
        N *= 5;
        if (N % 10 == 0){
          N /= 10;
        }
        N %= 10;
      }
    }
    if (cnt2 < cnt5){
      for (int i = 0; i < cnt5 - cnt2; i++){
        N *= 2;
        if (N % 10 == 0){
          N /= 10;
        }
        N %= 10;
      }
    }
    cout << N << endl;
  }
}