#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

long long gcd (long long s , long long t) { return t ? gcd(t,s%t) : s ; }

int divideNum(long long &n , int x){
    int cnt = 0 ;
    while(n % x == 0){
        cnt++;
        n /= x;
    }
    return cnt;
}

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

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

    int n2 = divideNum(M, 2), n5 = divideNum(M, 5);
    if(M != 1){
        cout<<-1<<endl;
    }else{
        while(N % 10 == 0){
            N /= 10;
        }
        N %= 10;

        int ten = max(n2, n5);
        while(n2 < ten) {
            N *= 2;
            while(N % 10 == 0) N /= 10;
            N %= 10;
            n2++;
        }
        while(n5 < ten) {
            N *= 5;
            while(N % 10 == 0) N /= 10;
            N %= 10;
            n5++;
        }
        cout<<N<<endl;
    }
        
    return 0;
}