class Screen(object):

def __init__(self,width=0,height=0):
    self._width = width
    self._height = height

@property
def width(self):
    return self._width

@width.setter
def width(self,value):
    self._width = value

@property
def height(self):
    return self._height

@height.setter
def height(self,value):
    self._height = value

@property
def resolution(self):
    return self._width * self._height