题解 | 合法IP

'''import sys
a=input().split('.')

def func(a):
    flag=0
    if len(a)==4:
        for i in a:
            if i :
                if int(i)>255 or int(i)<0:
                    flag+=1
                if str(int(i))!=i:
                    return ('NO')
            else:
                return ('NO')
    else:
        return ('NO')
    if(flag==0):
        return( 'YES')
    
    
    return ('NO')
print(func(a))'''
a=input().split('.')
def func():
    flag=0
    try:
        if(len(a)==4):
            for i in a:
                if int(i)>255 or int(i)<0:
                    return ('NO')
                if str(int(i))!=i:
                    return ('NO')
            else:
                return ('YES')
        else:
                return ('NO')
    except:
        return "NO"
b=func()
print(b)