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

Ex Input:
fCGEhfHvcRouHzNw, gtjBkhfHvcRouHee

Ex Output:
hfHvcRouH


Ex Input:
eFUexDIFlaPDUwrOb, mTvkKGUxDIFlaPDUwxGVpnIwbi

Ex Output:
xDIFlaPDUw


Ex Input:
BCHUQgkjLJzJbsP, wDlOaztuHUQgkjLJMl

Ex Output:

HUQgkjLJ