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

[EX Q]: lMRuEThD, wqQRuEKp
[EX A]: RuE

[EX Q]: jsXHot, gtXHmB
[EX A]: XH

[EX Q]: mKRZwBB, iBRZweZx
[EX A]:
RZw