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

Example Input: lQwpMQRxuVbJDv, UkzwpMQRxuDVT
Example Output: wpMQRxu

Example Input: yxJxNRLEnKGHziJtfb, KfReWhEnKGHzitzfPWzK
Example Output: EnKGHzi

Example Input: TLjkVpbsasi, bDjkVpbsoNVI
Example Output:
jkVpbs