Let's go the other direction. And yes, I guess I'd better say s not 2, or we're going to get an error here. Again, in twenty-three checks.

这里我得说不能是2，否则要报错了，再一次，调用了23次,在这个例子里，它从尾部开始。

麻省理工公开课 - 计算机科学及编程导论课程节选