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: AuSFmN, crSFXM
Example Output: SF

Example Input: FcteUjpoRSTpmZO, tAnjpoRSTFLQL
Example Output:
jpoRST