In this problem signs can be ignored in both initial and answer strings, so first we remove signs from initial strings. Then we make a list of the six possible concatenations of the 3 initial strings and convert all of them to lowercase.
For checking an answer string , we remove the signs , convert it to lowercase and check if it is just one of those 6 concatenations.
There were two really nice hack protocols , the first one is:
Here all concatenations become empty.
The second one was putting 0 as number of students :D