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

Example Input: mXHhaCEIwqwEZcz, JZPXbYHhaCEIwZmna
Example Output: HhaCEIw

Example Input: KKrCLvJKRoyV, WDeLvJKCBdS
Example Output: LvJK

Example Input: HgrFaVEc, SVJrFaIOu
Example Output:
rFa