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