# -*- coding: utf-8 -*
import math
n = int(input())
m = int(input())

g = math.gcd(n, m)
n //= g
m //= g

while n % 10 == 0:
    n //= 10
n %= 10

while m % 5 == 0:
    m //= 5
    n *= 2
    n %= 10
while m % 2 == 0:
    m //= 2
    n *= 5
    n %= 10

if m == 1:
    print(n)
else:
    print(-1)