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

if n%m == 0:
    ans = str(n//m)
    for s in ans[::-1]:
        if s != "0":
            print(s)
            exit()

g = math.gcd(n,m)
n //= g
m //= g
dic = {}
left = n
ans = 0
while left:
    ans = left//m
    left -= ans*m
    left *= 10
    if left in dic:
        print(-1)
        exit()
    dic[left] = 1
print(ans)