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

[EX Q]: OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO
[EX A]: QQnzOF

[EX Q]: iJbjApY, ggwbjAws
[EX A]: bjA

[EX Q]: hVQJkZyKfPoOQEukfAbXDpB, qpojyxWkZyKfPoOQEZkUI
[EX A]:
kZyKfPoOQE