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: GlAYDsKQoXy, IxDsKQuK
Example Output: DsKQ

Example Input: ESzrxHnfaZ, XWrxHndj
Example Output:
rxHn