题解 | #合法IP#

while True:
    try:
        ipNum=input().split(".")
        count = 0
        if len(ipNum)!=4:
            print("NO")
            continue
        for i in ipNum:
            if not i.isdigit():
                print("NO")
                continue
            elif int(i) >255 or (i.startswith('0') and len(i)>1) or int(i)<0:
                print("NO")
                continue
            else:
                count+=1
        if count == 4:
            print("YES")
    except:
        break