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

[EX Q]: zmbmQuyNGOe, mUMEmQuyiuS
[EX A]: mQuy

[EX Q]: kOrQWjLKnwN, xFsWjLKgr
[EX A]: WjLK

[EX Q]: kmYYxPx, lFGYYxwqW
[EX A]:
YYx