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

Example Input: CkZOSZevST, bbZOSZIg
Example Output: ZOSZ

Example Input: MSzHyOuaJILkeY, eUibEHoHyOuaJIhfvXy
Example Output: HyOuaJI

Example Input: VBZjhaNtXyLeauJQCn, whXxOJkkjhaNtXyLeaMiS
Example Output:
jhaNtXyLea