从键盘输入若干个学生的成绩，每个学生的成绩用逗号分隔开，例如56，89，99，90成绩输入完成时按回车键结束，然后分别统计低于60分的人数、60分到80分、80分到100分的人数，并且分别输出其结果，要求用子程序完成本实验。-Enter a number from the keyboard student achievement, student achievement for each separated by a comma, for example, 56,89,99,90 finished entering grades by the end of the Enter key, and then less than 60 points, respectively, the number of statistics, 60 assigned to 80, 80 assigned to the number 100, and output the result, require a subroutine to complete this study.