#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
ll n,m;

void solve(){
	ll g = gcd(n,m);
	n/=g;
	m/=g;
	ll M = m;
	int t = 0,f = 0;
	while(M%5==0)M/=5,f++;
	while(M%2==0)M/=2,t++;
	if(M!=1){
		cout<<-1<<endl;
		return;
	}
	while(n%10==0)n/=10;
	n%=10;
	if(f<t){
		for(int i = 0;i<t-f;i++){
			n*=5;
			n%=10;
		}
	}else{
		for(int i = 0;i<f-t;i++){
			n*=2;
			n%=10;
		}
	}
	cout<<n<<endl;

}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >> n >> m;
	solve();
}