题解 | #合法IP#

import sys

def IsValidIp(ip):
    if len(ip) != 4:
        return False
    for i in ip:
        if not (0 <= i <= 255):
            return False
    return True

for ip in sys.stdin.readlines():
    ip = [int(x) for x in ip.strip().split('.')]
    print("YES" if IsValidIp(ip) else "NO")