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: RtAchtNymcswVk, FWRuRchtNymcswUkoERHyML
Example Output: chtNymcsw

Example Input: bSpZiq, QppZOf
Example Output:
pZ