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

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

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

[EX Q]: ijokGCrdF, MGXkGCVRf
[EX A]:
kGC