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

Ex Input:
HXYkGv, GCYksu

Ex Output:
Yk


Ex Input:
JzbEpAquDJFKcNvEWZxVqRV, PFiJlpAquDJFKcNcqOpMeAv

Ex Output:
pAquDJFKcN


Ex Input:
mmPxNhRPZn, zHVxNhRaJW

Ex Output:

xNhR