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

Ex Input:
JIOKyo, oPOKsX

Ex Output:
OK


Ex Input:
iYSNsY, HSSNhP

Ex Output:
SN


Ex Input:
IszIZBRtvMzuGfwWqZh, DIYyoyRtvMzuGfwnHyW

Ex Output:

RtvMzuGfw