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: elloYaejTczBiiNOU, XoCPzloYaejTcXYtKODL
Example Output: loYaejTc

Example Input: qHHLZmesRfUwqDK, AHZmesRfUwJXXXlPng
Example Output:
ZmesRfUw