题解 | 合法IP

import sys

for line in sys.stdin:
    s = line.strip().split(".")
    if len(s) != 4:
        print("NO")
        break
    for i in s:
        if i =='' :
            print('NO')
            break
        if i.isdigit:
            if int(i) < 0 or int(i) > 255 or len(str(int(i)))!=len(i):
                print("NO")
                break
        else:
            print("NO")
            break
    else:
        print('YES')