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

Example Input: edjRAatlaiCmWkpqMh, qDZYVWCDTRAatlaiCmYH
Example Output: RAatlaiCm

Example Input: wrVsKN, mOVsWo
Example Output: Vs

Example Input: KviBhCXYzmNDUYth, SOZKBBhCXYzmQy
Example Output:
BhCXYzm