def gcd(n, m):
    if m == 0:
        return n
    return gcd(m, n % m)

def main():
    N = int(input())
    M = int(input())
    g = gcd(N, M)

    N //= g
    M //= g
    while N % 10 == 0:
        N = N // 10
    N %= 10

    while M % 5 == 0:
        M = M // 5
        N *= 2
        N %= 10

    while M % 2 == 0:
        M = M // 2
        N *= 5
        N %= 10

    if M == 1:
        print(N)
    else:
        print(-1)

if __name__ == '__main__':
    main()