蓝桥杯算法提高VIP-数字黑洞-题解（Python代码）

想问一下，究竟是哪里出错了？

N = input()
i =1
s_num = set(str(N))
l_num_j = []
# print(num)
if len(s_num) == 4:
    while 1:
        l_num_s = list(s_num)
        l_num_s.sort(reverse=True)
        l_num_j = l_num_s[::-1]

        num1 = int(''.join(l_num_s))
        num2 = int(''.join(l_num_j))

        num = num1 - num2
        # print(num1, num2,num)
        if num != 6174:
            i = i+1
            s_num = str(num)
            continue
        else:
            print(i)
            break