#!/usr/bin/env python3
#-*- coding: utf-8 -*-

class Screen(object):

    @property
    def width(self):
        return self.__width

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

    @width.setter
    def width(self, value):
        if not isinstance(value, (int, float)):
            raise ValueError('width must be a number!')
        elif value < 0:
            raise ValueError('width must be > 0!')
        else:
            self.__width = value

    @height.setter
    def height(self, value):
        if not isinstance(value, (int, float)):
            raise ValueError('height must be a number!')
        elif value < 0:
            raise ValueError('height must be > 0!')
        else:
            self.__height = value

    @property
    def resolution(self):
        self.__resolution = self.__height * self.__width
        return self.__resolution