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

Example Input: AeYjeKwZQillzpD, SnqviKwZQillrxuTB
Example Output: KwZQill

Example Input: OVZxWYzAAxG, rStOxWYzJeoC
Example Output: xWYz

Example Input: TEouepfyDNFP, bapfyDNMyUQ
Example Output:
pfyDN