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

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

Int gcd(Int a, Int b) {
	return b == 0 ? a : gcd(b, a % b);
}

int f(int n, int p) {
	int c = 0;
	while (n > 0 && n % p == 0) {
		n /= p;
		c++;
	}
	return c;
}

Int N, M;
int main() {
	cin >> N >> M;
	Int g = gcd(N, M);
	N /= g;
	M /= g;

	Int m = M;
	int two = 0, five = 0;
	while (m > 0 && m % 2 == 0) {
		m /= 2;
		two++;
	}
	while (m > 0 && m % 5 == 0) {
		m /= 5;
		five++;
	}
	if (m != 1) {
		cout << -1 << endl;
	}
	else {
		Int ans = N;
		while (ans % 10 == 0) ans /= 10;
		ans %= 10;
		REP(i, two) {
			ans *= 5;
			while (ans % 10 == 0) ans /= 10;
			ans %= 10;
		}
		REP(i, five) {
			ans *= 2;
			while (ans % 10 == 0) ans /= 10;
			ans %= 10;
		}
		cout << ans << endl;
	}
}