from math import gcd

n = int(input())
m = int(input())
g = gcd(n, m)
n //= g
m //= g
two = 0
five = 0
while m % 2 == 0:
    m //= 2
    two += 1
while m % 5 == 0:
    m //= 5
    five += 1
if m != 1:
    print(-1)
else:
    while n % 10 == 0:
        n //= 10
    ans = n % 10
    if two > five:
        for _ in range(two - five):
            ans *= 5
            ans %= 10
    else:
        for _ in range(five - two):
            ans *= 2
            ans %= 10
    print(ans)