N, M = int(input()), int(input())

def to_and_five(num, lists=[]):
    if num == 1:
        return lists
    if num % 2 == 0:
        return to_and_five(num // 2, lists + [2])
    if num % 5 == 0:
        return to_and_five(num // 5, lists + [5])
    return False

def prime(n, m):
    for i in range(2, int(min(m, n) ** 0.5) + 1):
        if n % i == 0 and m % i == 0:
            return prime(n // i, m // i)
    return n, m

if N % M == 0:
    ans = N // M
    while not ans % 10:
        ans //= 10
else:
    N, M = prime(N, M)
    if (tmp := to_and_five(M)):
        N %= 10
        for i in tmp:
            if i == 5:
                N *= 2
            else:
                N *= 5
            N %= 10
        ans = N
    else:
        ans = -1
print(ans)