随机发生器，学校。例如，如果用户选择0431类，使用O。

代码说明：

随机学号发生器。如，如果用户选择0431班，使用序号为1，那么随机给出0431班中除了学号为1～10之外的其它所有学号中的n个学号；如果选择2，那么随机给出除了学号为10～20之间的其它n个学号；依次类推。-random generator, school. For example, if the user selects 0431 class, the use of a serial number. then randomly given 0,431 school classes, in addition to a 10-all other outside the school, the school n; If you choose two, then were given school, in addition to between 10 ~ 20 other school n; followed by analogy.