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

Q: YRNpKFPGzUsgCOBJgbVG, TdEpMngFPGzUsgCOZykYRrLp

A: FPGzUsgCO
****
Q: feYKRk, PrYKMW

A: YK
****
Q: ZkPWLgFDHqmUoeSPxWC, dXMLgFDHqmUovkNtqYtQM

A:
LgFDHqmUo
****