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

Example Input: dmigbcBoWdAIyaeE, zXiKQFbcBoWdAIyaEypIjJpwbU
Example Output: bcBoWdAIya

Example Input: atDgsOWuP, UJMgsOrwj
Example Output: gsO

Example Input: VfDmeIsKjdmcm, fjmeIsKMVn
Example Output:
meIsK