In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

[EX Q]: RyaNyUvXAaZHLXUtYuz, CkbsWxZyUvXAaZHLXJJzugDy
[EX A]: yUvXAaZHLX

[EX Q]: AuSFmN, crSFXM
[EX A]: SF

[EX Q]: ytKyEZrpSimvb, cofdZrpSiAL
[EX A]:
ZrpSi