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: jFVaEHbMrrkW, ekfVaEHbPnBnM
Example Output: VaEHb

Example Input: geeDibeoIpt, BXnMBDibeoEn
Example Output:
Dibeo