#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

map<ll, ll>prime_factor(ll N){
    map<ll, ll>ret;
    for(ll i = 2; i * i <= N; i++){
        while(N % i == 0){
            ret[i]++;
            N /= i;
        }
    }
    if(N != 1)ret[N] = 1;
    return ret;
}


int main(){

    ll N, M;
    cin >> N >> M;
    map<ll, ll>mp;
    for(ll i = 2; i * i <= M; i++){
        while(M % i == 0){
            mp[i]--;
            M /= i;
        }
    }
    if(M != 1)mp[M]--;
    for(ll i = 2; i * i <= N; i++){
        while(N % i == 0){
            mp[i]++;
            N /= i;
        }
    }
    if(N != 1)mp[N]++;
    while(mp[2] < 0 || mp[5] < 0){
        mp[2]++;
        mp[5]++;
    }
    ll ans = 1;
    for(auto it = mp.begin(); it != mp.end(); it++){
        if((*it).second < 0){
            cout << -1 << endl;
            return 0;
        }
        for(ll i = 0; i < (*it).second; i++){
            ans *= (*it).first;
            while(ans % 10 == 0)ans /= 10;
            ans %= 10;
        }
    }
    cout << ans << endl;

    return 0;
}