#!/usr/bin/python3
from fractions import gcd

n, m = int(input()), int(input())
g = gcd(n, m)
n //= g
m //= g

c2, c5 = 0, 0
while m % 2 == 0:
    m //= 2
    c2 += 1
while m % 5 == 0:
    m //= 5
    c5 += 1

if m != 1:
    print(-1)
    exit(0)

if c2 > c5:
    n *= 5**(c2-c5)
elif c2 < c5:
    n *= 2**(c5-c2)

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

res = n % 10
print(res)