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

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define ll long long
#define ull unsigned ll

template<class T> T GCD(T a,T b){T r; while(a){r=b; b=a; a=r%a;} return b;}

int main(){
  int i, j, k;
  int p2 = 0, p5 = 0;
  ull N, M, g;

  scanf("%llu%llu",&N,&M);
  g = GCD(N,M);
  N /= g; M /= g;

  while(M%2==0) M/=2, p2++;
  while(M%5==0) M/=5, p5++;
  if(M>1){ puts("-1"); return 0; }

  while(N%10==0) N /= 10;
  N %= 10;
  while(p2>p5) p5++, N=(N*5)%10;
  while(p2<p5) p2++, N=(N*2)%10;

  printf("%d\n",(int)N);

  return 0;
}