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

Example Input: yywhNdZQkLSzbOvhluicHA, lfZQkLSzbOvhVC
Example Output: ZQkLSzbOvh

Example Input: LJJvLTK, jpFJvLqh
Example Output: JvL

Example Input: cCDTMXjGMNikONun, jpcMXjGMNizBEWQzT
Example Output:
MXjGMNi