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

Ex Input:
umXfmRnUgALpFAqBaKfNfo, aOAXWnUgALpFAqBmNpTCdj

Ex Output:
nUgALpFAqB


Ex Input:
PGjDRPDzGaBR, rpIJRPDzWi

Ex Output:
RPDz


Ex Input:
azOwvxxNgDugSX, RaDxxNgDRbhNK

Ex Output:

xxNgD