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

Ex Input:
krnkpodgfpCKtfCqyzUbymWbxi, DydgSWpCKtfCqyzDaMsjqc

Ex Output:
pCKtfCqyz


Ex Input:
hGyDyQYdxCCuD, BQiFOyQYdxel

Ex Output:
yQYdx


Ex Input:
ecfsfw, XofsHN

Ex Output:

fs