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

Example Input: AedXEOrEgvnzF, TVTEOrEgvxKuJgv
Example Output: EOrEgv

Example Input: rszjOPpbXm, pnBujOPpWHz
Example Output: jOPp

Example Input: NnCmCAFfYhNQZkrGJjkepJzd, WKColPSCAFfYhNQZkOL
Example Output:
CAFfYhNQZk