从键盘输入一个班（全班最多不超过30人）学生某门课的成绩，当输入成绩为负值时，输入结束，分别实现下列功能：　
（1）统计不及格人数并打印不及格学生名单；　
（2）统计成绩在全班平均分及平均分之上的学生人数，并打印这些学生的名单；
（3）统计各分数段的学生人数及所占的百分比。(Enter a class from the keyboard (no more than 30 people in the class). When the input results are negative, the input is finished, and the following functions are realized, respectively.

(1) failing to pass statistics and failing to pass the list of students.

(2) to count the number of students above the average and the average scores, and print the list of these students.

(3) statistics of the number of students in each score and percentage.)