n = input()
n = list(n)
if n[0] == n[1] == n[2] == n[3]:
    print("N - N = 0000")
n1 = n[:]
n2 = n[:]
while int(''.join(n1)) - int(''.join(n2)) != int(''.join(n)):
    for j in range(len(n) - 1):
        for i in range(len(n) - 1 - j):
            if n1[i] <= n1[i + 1]:
                b = n1[i]
                n1[i] = n1[i + 1]
                n1[i + 1] = b
            if n2[i] >= n2[i + 1]:
                a = n2[i]
                n2[i] = n2[i + 1]
                n2[i + 1] = a
    if int(''.join(n1)) - int(''.join(n2)) ==int(''.join(n)):
        break
    print("{} - {} = {}".format(''.join(n1), ''.join(n2), int(''.join(n1)) - int(''.join(n2))))

    n = list(str(int(''.join(n1)) - int(''.join(n2))))
    n1 = n[:]
    n2 = n[:]

总是有点小问题 求解答啊