class Screen(object):

    @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