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):

        if not isinstance(value, int):

            raise ValueError('width must be an integer!')

        if value < 0:

            raise ValueError('width must more 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('height must more than 0!')

        self._height = value

    @property

    def resolution(self):

        return self._width * self._height