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

[EX Q]: CiElmOvTqJGVJkfSaDRzE, EjDJwMyxTvTqJGVJkfluB
[EX A]: vTqJGVJkf

[EX Q]: RMurrwPjlfG, QBKrrwPDkTM
[EX A]: rrwP

[EX Q]: mCxQTIaXN, mWQTIaxzPT
[EX A]:
QTIa