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

Example Input: CwTYJWQbzEZkvcqKn, hBnhJWQbzEZkKmVM
Example Output: JWQbzEZk

Example Input: UldKHMpUYADGfEUGcSon, nPHMpUYADGfEKqHCLPmL
Example Output: HMpUYADGfE

Example Input: VEddIQxt, KDddIWN
Example Output:
ddI