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

Example Input: pIkAtJHVcvzzZVz, btWerNSHVcvzzZTz
Example Output: HVcvzzZ

Example Input: srPyjmTQhdFFMcQ, QQGBdtyjmTQhmfEy
Example Output: yjmTQh

Example Input: YOHegQKoBpTnMb, oaVQKoBpFkVa
Example Output:
QKoBp