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: WjyKtxKtEYjP, vuBZJZyKtxKtXRZs
Example Output: yKtxKt

Example Input: PLONPdaFm, PaoONPdaVDi
Example Output:
ONPda