N = int(input())
M = int(input())
two, five = 0, 0
while N % 2 == 0:
    N //= 2
    two += 1
while N % 5 == 0:
    N //= 5
    five += 1
while M % 2 == 0:
    M //= 2
    five += 1
while M % 5 == 0:
    M //= 5
    two += 1
    
two, five = two - min(two, five), five - min(two, five)
if N % M != 0:
    print(-1)
    exit()
N //= M
ans = N % 10 * pow(2, two, 10) * pow(5, five, 10) % 10
print(ans)