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

[EX Q]: fCGEhfHvcRouHzNw, gtjBkhfHvcRouHee
[EX A]: hfHvcRouH

[EX Q]: hRVyvwHqnN, geHeyvwHqiBiYJ
[EX A]: yvwHq

[EX Q]: UxHWsFXGSvIe, ORrOWsFXGDkxx
[EX A]:
WsFXG