统计学生成绩：设有20个学生的成绩（可以自己规定分数），试编写程序分别统计低于60分，60~69，70~79，80~89，90~99分及100分的人数，并存放到S1，S2，S3，S4，S5，S6单元中-Statistics student achievement: student achievement with 20 (you can set himself points), try to program statistics less than 60 minutes, respectively, 60 ~ 69,70 ~ 79,80 ~ 89,90 ~ 99 points and 100 points, the number of co-exist into the S1, S2, S3, S4, S5, S6 units