class Screen(object):
    @property
    def width(self):
        return self._width



    @width.setter
    def width(self, value):
        if not isinstance(value, int):
            raise ValueError('width must be an integer')
        if value < 0:
            raise ValueError('width must be non-negative')
        self._width = value



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



    @height.setter
    def height(self, value):
        if not isinstance(value, int):
            raise ValueError('height must be an integer')
        if value < 0:
            raise ValueError('height must be non-negative')
        self._height = value



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