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

[EX Q]: yRhCObvPZYoKUoQnyaatR, NHzLJYPZYoKUoQnJnIsZxC
[EX A]: PZYoKUoQn

[EX Q]: KKrCLvJKRoyV, WDeLvJKCBdS
[EX A]: LvJK

[EX Q]: OsIlBZLIyQsvYWVjzoZB, NtwThyQsvYWVjSwcgSc
[EX A]:
yQsvYWVj