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

Example Input: eNuawupVqQ, RIawuplUIf
Example Output: awup

Example Input: bUcuzFgsdfojVR, IdcuzFgsdMRgtMA
Example Output: cuzFgsd

Example Input: eDYhpsxRtMFzfD, avCspsxRtTPp
Example Output:
psxRt