/* -*- coding: utf-8 -*-
 *
 * 25.cc: No.25 有限小数 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

ll gcd(ll m, ll n) {
  if (m < n) swap(m, n);
  while (n > 0) {
    ll r = m % n;
    m = n;
    n = r;
  }
  return m;
}

/* main */

int main() {
  ll n, m;
  cin >> n >> m;

  ll g = gcd(m, n);
  m /= g;
  n /= g;
  
  int n2 = 0, n5 = 0;
  while (m % 2 == 0) m /= 2, n2++;
  while (m % 5 == 0) m /= 5, n5++;
  //printf("n2=%d, n5=%d\n", n2, n5);

  if (m != 1) {
    puts("-1");
    return 0;
  }

  while (n % 10 == 0) n /= 10;
  int d = n % 10;

  while (n2 < n5) {
    d *= 2;
    while (d % 10 == 0) d /= 10;
    d %= 10;
    n2++;
  }
  while (n2 > n5) {
    d *= 5;
    while (d % 10 == 0) d /= 10;
    d %= 10;
    n5++;
  }

  printf("%d\n", d);
  return 0;
}