如何使用dynamic_cast获取对象类型？

I am doing a homework, and I am stuck in something: I've done everything, but there is a function in specific class, that I didn't know how to implement. I have a class named A let's say, and two classes that inherit from A, let's call them B and C. So basically main class is A, and inherit classes are B and C, and I have a set of elements for these types (set of pointers for A), I am doing a homework, and I am stuck in someth