说明：  从键盘接收输入的一个班的学生成绩，并存放于50字grade数组中，其中grade+i保存学号为i+1的学生成绩。然后根据grade中的学生成绩，把学生名次填入50字rank字数组中，其中 rank+i的内容是学号为i＋1学生的名次。再按学号顺序把名次从终端上显示出来。(输入学生个数<=50，可以不定)
(Receive input from the keyboard of a class of student achievement, and stored in 50 words grade array, which grade+ I save school No. i+ 1 of student achievement. And then under the grade of student achievement, the students fill in 50 words rank ranking word group, which rank+ I is the number school students rank i 1. And then places the order of the rankings from No. terminals displayed. (Enter student number )