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

Example Input: VGRjWGHRcBdFmkVg, eSwqALQXWGHRcBdFsDXCM
Example Output: WGHRcBdF

Example Input: JzbEpAquDJFKcNvEWZxVqRV, PFiJlpAquDJFKcNcqOpMeAv
Example Output: pAquDJFKcN

Example Input: IWwtBIJaQNPCVDFzZpLoVaBiF, YzUkUNJaQNPCVDFzENGRBH
Example Output:
JaQNPCVDFz