I recently stumbled upon this beautiful problem, but I didn't manage to solve it and I don't have a clue about its solution.

It basicaly asks you to count the number of pairs (s, t), where s and t are strings and t is a substring of s. Size of s is N (N <= 200) and size of t is M (M <= 50), also the alphabet size is A (A <= 1000).

This is the link to the contest.

I will greatly appreciate any ideas on how to solve this problem and if you know some similar problems, please let me know.

Thanks in advance!