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

Example Input: OhMVLbQhBxEaOZY, iDVLbQhBxBiiD
Example Output: VLbQhBx

Example Input: wLLwjL, arLwXm
Example Output: Lw

Example Input: RPrGecsDePDshdv, DukzorGecsDeTj
Example Output:
rGecsDe