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

Example Input: VRXUhOYfTul, JqZUhOYKq
Example Output: UhOY

Example Input: biAihydBoNlzR, IAloNhydBolwUz
Example Output: hydBo

Example Input: hvorif, FXorQD
Example Output:
or