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