def gcd(x, y):
    if y == 0:
        return x
    return gcd(y, x % y)
N = int(input())
M = int(input())
d = gcd(N, M)
N //= d
M //= d
a2, a5 = 0, 0
while M % 2 == 0:
    a2 += 1
    M //= 2
while M % 5 == 0:
    a5 += 1
    M //= 5
if M != 1:
    print("-1")
else:
    while N % 10 == 0:
        N //= 10
    ret = N % 10
    for i in range(a2):
        ret = (ret * 10) // 2
        if ret % 10 == 0:
            ret /= 10
        ret = ret % 10
    for i in range(a5):
        ret = (ret * 10) // 5
        if ret % 10 == 0:
            ret //= 10
        ret = ret % 10
    print(ret)