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

[EX Q]: faHRBWyXsYzYmHQyy, aHTyXsYzYeXBFV
[EX A]: yXsYzY

[EX Q]: UvYbfKFybXofcwLRrLRiK, BgMZKFybXofcVe
[EX A]: KFybXofc

[EX Q]: HGMWGHitEkCRigRzjKzZ, MfPuuooagHHitEkCRigRoDNQXWG
[EX A]:
HitEkCRigR