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

Example Input: DFRoMPNDAzNgtLsEPseOzC, qykyPjDAzNgtLsEPYTsNrJaNK
Example Output: DAzNgtLsEP

Example Input: LudFxiaqbX, UWMPnFxiaqikiDx
Example Output: Fxiaq

Example Input: wiaWitMYoaQ, TCSnaWitMYIN
Example Output:
aWitMY