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('score must big than 0 !')
        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('score must big than 0 !')
        self._height = value
    @property
    def resolution(self):
        return self._height * self._width