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

[EX Q]: feYKRk, PrYKMW
[EX A]: YK

[EX Q]: BUvWkxrAvDQG, rHrkxrAkCE
[EX A]: kxrA

[EX Q]: RNpWCCAKOeBPWKvVn, YDWCCAKOeBFgYwYW
[EX A]:
WCCAKOeB