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

Example Input: TnbLNKnNSs, NhDLNKnNRd
Example Output: LNKnN

Example Input: TdvkBvVyJcSdYGGPfnyml, rIvIvVyJcSdYhtxG
Example Output: vVyJcSdY

Example Input: QCeKdd, RKeKIP
Example Output:
eK