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

Ex Input:
lkFGXvTkKm, wwELXvTkcOnG

Ex Output:
XvTk


Ex Input:
mQvintdwLUpClREgxv, rYnoXBtdwLUpClRwxsqX

Ex Output:
tdwLUpClR


Ex Input:
YwqfsBcFziuLLjLdE, OeNamcFziuLpfJhtv

Ex Output:

cFziuL