题解 | #合法IP#

while True:
    try:
        str1 = input().split(".")
        flag = 0
        if len(str1) == 4:
            for i in str1:
                if (len(i) > 1 and i[0] != '0') or len(i) == 1:
                        if i.isdigit() and 0 <= int(i) <= 255:
                            flag += 1
        
        if flag == 4:
            print('YES')
        else:
            print('NO')
    
    except:
        break