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

Example Input: HiEuutntEBpU, fdkqEuutntEBABdGZRND
Example Output: EuutntEB

Example Input: CdRbREFMEDTXnEzgn, zHLEMMEDTXnEPH
Example Output: MEDTXnE

Example Input: IKoFolFwPfDQKZXGTJk, HGpiZslFwPfDQKZRhMshHtq
Example Output:
lFwPfDQKZ