import math

def gcd(n, m):
    if m == 0:
        return n
    return gcd(m, n % m)

n = int(input())
m = int(input())

g = gcd(n, m)

n = n // g
m = 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(int(n))
else:
    print(-1)