题解 | #合法IP#

try:  # 就通过显示的用例一点一点加条件
    res = 'YES'
    stri = input().split('.')
    for i in stri:
        if i[0] == "0" and len(i)>1:
            res = 'NO'

    for i in stri:
        if not i[0].isdigit():
            res = "NO"
    arr = list(map(int ,stri))


    if len(arr)!=4:
        res = 'NO'

    for i in arr:
        if not 0<=i<=255:
            res = "NO"

    print(res)  
except:
    print('NO')