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

Example Input: XSnVeAjWLFWTgwmf, WsByLAjWLFWnQfl
Example Output: AjWLFW

Example Input: BrDGrTD, PBHDGrDw
Example Output: DGr

Example Input: BVRTCzOh, OTpTCzgB
Example Output:
TCz

