题解 | 合法IP

import sys

l = list(input().split('.'))
def isIP(x):
    if len(x) != 4:
        return 'NO'
    for i in x:
        if not i.isdigit():
            return 'NO'
    for i in x:
        if i[0] == '0' and int(i) != 0:
            return 'NO'
        if not 0 <= int(i) <= 255:
            return 'NO'
    return 'YES'

print(isIP(l))