定义一个Student类，在该类定义中包括：一个数据成员score（分数）及两个静

态数据成员total（总分）和学生人数count；成员函数scoretotalcount(float s) 用于设置分数、求总分和累计学生人数；静态成员函数sum()用于返回总分；静态成-Define a Student class, the class definition including: a data member score (points) and two static data members of the total (Total) and the number of students count　member function scoretotalcount (float s) used to set the score, find the total score and the total number of students　static member function sum () to return Total　static into