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

Example Input: nxoXDohHr, WcbkXDohFbJ
Example Output: XDoh

Example Input: NTINFnRckGsfLqhSoA, UUONcKKFnRckGsfLqVak
Example Output: FnRckGsfLq

Example Input: PBZjgZ, orZjll
Example Output:
Zj