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

Example Input: nhGinCtvLartcMPhJwGRbpZNrq, iQJlFKayEartcMPhJwDRROB
Example Output: artcMPhJw

Example Input: QaxEaxdouNyyvNAn, wRjWSaxdouNyyrriQiG
Example Output: axdouNyy

Example Input: zlvZlFkyumErMCUXvsk, MKPRZlFkyumEUS
Example Output:
ZlFkyumE