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

Example Input: KfjqnJLciTXqkJK, yqfRcfqnJLcisSB
Example Output: qnJLci

Example Input: kWTQrtCaoTbXIiXDphMG, pLhxkfeDoTbXIiXDpCCzTYyZv
Example Output: oTbXIiXDp

Example Input: KviBhCXYzmNDUYth, SOZKBBhCXYzmQy
Example Output:
BhCXYzm

