定义一个立方体类，包含的数据成员有立方体的左上角坐标位置和右下角坐标位置，并实现如下要求。

要求：　　1）构造函数带入两个三维坐标点位置来初始化成员变量；

　　　　2）另一个构造函数带入一个坐标点位置和一个边长来构造一个正方体；

　　　　3）一个成员函数求立方体的中心；

　　　　4）一个成员函数来获取立方体的体积和表面积；

　　　　5）添加静态成员变量统计当前有多少个对象处于生存期，添加静态成员变量表示一个生成过多少个对象；

　　　　6）添加静态成员函数获取上面的两个静态成员变量。

　　7）要有主函数测试所写的功能。-Define a cube class contains data members are left coordinate position and the coordinate position of the lower right corner of the cube, and to achieve the following requirements.

Requirements: 1) into the two-dimensional coordinates constructor to initialize member variables point　

2) another constructor into a coordinate position and a side to construct a cube　

3) A member function evaluation center of the cube　

4) a member function to get the cube of volume and surface area　

5) Add a static member variable statistics how many objects are in the current lifetime, add a static member variable represents a generation how many objects　

6) Add a static member function to get the above two static member variables.

7) The main function tests have written functions.