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

[EX Q]: vytthSjj, XVttthSFAvk
[EX A]: tthS

[EX Q]: zeuyZKwvIOfx, BlmZKwvspUt
[EX A]: ZKwv

[EX Q]: kDHmzgPzGe, CBzgPzWcD
[EX A]:
zgPz