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

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

[EX Q]: YHLJZrFQ, aSLJZQuo
[EX A]: LJZ

[EX Q]: VKZdDmWjzb, HReZdDmmk
[EX A]:
ZdDm