题解 | #合法IP#

import sys

for line in sys.stdin:
    a = line.strip().split('.')
    try:
        if len(a) != 4:
            print('NO')
        else:
            for i in range(4):
                if (0<=int(a[i])<=255 
                and len(str(int(a[i]))) == len(a[i])):
                    continue
                else:
                    print('NO')
                    break
            else:
                print('YES')
    except:
        print('NO')