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

Ex Input:
OjQHcFUCflYUptUPqYKVomn, GXHcFUCflYUpSSTrQ

Ex Output:
HcFUCflYUp


Ex Input:
lkFGXvTkKm, wwELXvTkcOnG

Ex Output:
XvTk


Ex Input:
wXGerDNhSNnCCedyzskswVnh, BfFNhSNnCCedybrUbI

Ex Output:

NhSNnCCedy