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

Example Input: ezVsFayUPcrte, lfsFayUMPTqx
Example Output: sFayU

Example Input: yxJxNRLEnKGHziJtfb, KfReWhEnKGHzitzfPWzK
Example Output: EnKGHzi

Example Input: JdNOrFdQMjE, UmgArFdQZIA
Example Output:
rFdQ