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

Example Input: NTINFnRckGsfLqhSoA, UUONcKKFnRckGsfLqVak
Example Output: FnRckGsfLq

Example Input: tmBlKUto, eFDBlKLy
Example Output: BlK

Example Input: uCxJGrDAOYfnmLLkrXPn, fXVqDAOYfnmLxfzQv
Example Output:
DAOYfnmL