题解 | #牛客网的IP地址#
牛客网的IP地址
https://www.nowcoder.com/practice/b4159a20aefa406aaa1bfd7d9739c70c
使用flag作标签，如有非法特征，flag = ‘illegal’，最后print（flag）即可
s = input().split('.')
flag = 'legal'
if len(s) != 4:
flag = 'illegal'
else:
for i in s:
if i:
if int(i) > 255 or int(i) < 0:
flag = 'illegal'
else:
flag = 'illegal'
print(flag)
