import math
n = int(input())
m = int(input())

if n%m == 0:
    ans = n//m
    while ans%10 == 0:
        ans //= 10
    print(ans%10)
    exit()

two = 0
five = 0
nm = m
while m%5 == 0:
    m //= 5
    five += 1
while m%2 == 0:
    m //= 2
    two += 1

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

n *= 5**two
n *= 2**five

ans = n
while ans%10 == 0:
    ans //= 10
print(ans%10)