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

[EX Q]: atDgsOWuP, UJMgsOrwj
[EX A]: gsO

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

[EX Q]: qOvARLrBqN, NWKQRLrBRivm
[EX A]:
RLrB