题解 | #合法IP#

while True:
    try:
        N = str(input())
        ls = N.split(".")
        state = "YES"
        if len(ls) != 4:
            state = "NO"
        for i in ls:
            if i=="":
                state = "NO"
                continue
            if i.startswith('0') and len(i) > 1:
                state = "NO"
                continue
            if not i.isdigit():
                state = "NO"
                continue
            if int(i) < 0:
                state = "NO"
                continue
            if int(i) > 255:
                state = "NO"
                continue
        print(state)
    except:
        break