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:
mRVieYomZqJXaTDsShCyfPW, ifOAlnptmZqJXaTDsVMqY

Ex Output:
mZqJXaTDs


Ex Input:
XAdMwHASaYpwWuwFFX, KBWGQHASaYpwWuLwB

Ex Output:

HASaYpwWu