编写C++程序完成以下功能：

（1）　　定义一个Point类，其属性包括点的坐标，提供计算两点之间距离的方法；

（2）　　定义一个矩形类，其属性包括左上角和右下角两个点，提供计算面积的方法；

（3）　　创建一个矩形对象，提示用户输入矩形左上角和右下角的坐标；

（4）　　观察矩形对象以及Point类成员的构造函数与析构函数的调用；

（5）　　计算其面积，并输出。

-Write C++ program performs the following functions: (1) defines a Point class, its properties include the coordinates of points, providing methods of calculating the distance between two points　(2) define a rectangle class, its properties include the two top left and bottom right corner points, provided the method calculates the area　(3) create a rectangle object, the user is prompted top left and bottom right coordinates of the rectangle　(4) observed a rectangular object, and a member of the Point class constructor and destructor calls　(5 ) to calculate the area and output.