#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

ll mod_pow(ll x, ll n, ll mod){
  ll res = 1;
  while(n>0){
    if(n&1) res = res*x%mod;
    x = x*x%mod;
    n >>= 1;
  }
  return res;
}
ull gcd(ull a, ull b){return (b==0?a:gcd(b,a%b));}

int main(){
  ull N, M;
  cin >> N;
  cin >> M;

  ull g = gcd(N,M);
  N/=g;
  M/=g;

  int cnt2=0, cnt5=0;
  while(M%2==0){
    M/=2;
    cnt2++;
  }
  while(M%5==0){
    M/=5;
    cnt5++;
  }
  if(M!=1){
    cout << -1 << endl;
    return 0;
  }

  while(N%10==0) N/=10;
  N%=10;

  int mx = max(cnt2, cnt5);
  cnt2 = mx - cnt2;
  cnt5 = mx - cnt5;
  
  ull ret = N;
  while(cnt2>0){
    ret *= 2;
    ret %= 10;
    cnt2--;
  }
  while(cnt5>0){
    ret *= 5;
    ret %= 10;
    cnt5--;
  }
  cout << ret << endl;
  
  return 0;
}