#include<iostream>
using namespace std;
typedef long long ll;

bool check(ll m){
    while(m % 5 == 0)   m /= 5;
    while(m % 2 == 0)   m /= 2;
    return m == 1;
}

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

    if(!check(m)){
        cout << -1 << endl;
        return 0;
    }

    ll ans = 0;
    while(n){
        ans = n/m;
        n %= m;
        n *= 10;
    }

    if(ans >= 10){
        ll ten = 10;
        while(ans%ten == 0) ten*=10;
        ans = (ans%ten)*10/ten;
    }

    cout << ans << endl;
    
    return 0;
}