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

Example Input: QaxEaxdouNyyvNAn, wRjWSaxdouNyyrriQiG
Example Output: axdouNyy

Example Input: STvKOHq, XMGvKOdyM
Example Output: vKO

Example Input: BCaChdcQSWgCYXQR, uaxDkZrtChdcQSWgCeQzFrc
Example Output:
ChdcQSWgC