#!/usr/bin/env python3

import math


IMPOSSIBLE = -1


def solve(n, m):
    g = math.gcd(n, m)
    n //= g
    m //= g
    f2 = 0
    f5 = 0
    while m % 2 == 0:
        m //= 2
        f2 += 1
    while m % 5 == 0:
        m //= 5
        f5 += 1
    if m > 1:
        return IMPOSSIBLE
    while n % 10 == 0:
        n //= 10
    n %= 10
    while f2 > f5:
        f5 += 1
        n = n * 5 % 10
    while f2 < f5:
        f2 += 1
        n = n * 2 % 10
    return n


def main():
    print(solve(int(input()), int(input())))


if __name__ == '__main__':
    main()