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

Example Input: XqyPjqNZDEK, EfwPjqNgjIP
Example Output: PjqN

Example Input: OhMVLbQhBxEaOZY, iDVLbQhBxBiiD
Example Output: VLbQhBx

Example Input: HzxQwlQhjDtGjs, OJgtwlQhjBlS
Example Output:
wlQhj