题解 | #合法IP#

while 1:

    try:

        ip = input().split('.')

        flag = 'YES'

        if len(ip)!=4:

            flag = 'NO'

        for i in ip:

            if not i.isdigit():

                flag = 'NO'

                break

            elif int(i)<0 or int(i)>255 or (len(i)>1 and i[0]=='0'):

                flag = 'NO'

                break

        print(flag)

    except:

        break