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

Example Input: nxTtNYaazlOyEBApiUSJS, BLazlOyEBCV
Example Output: azlOyEB

Example Input: TnbLNKnNSs, NhDLNKnNRd
Example Output: LNKnN

Example Input: TYuRcBIJXQCqO, MFBIJXQwtrD
Example Output:
BIJXQ