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]: UTdardKNThdYrGKMqZPeg, mvrThdYrGKMlcCxBtak
[EX A]: ThdYrGKM

[EX Q]: dnaTxyikMY, dUaTxyBRE
[EX A]:
aTxy