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

Ex Input:
vytthSjj, XVttthSFAvk

Ex Output:
tthS


Ex Input:
aWshKwEuYBBdSwIAyXw, wfVuYBBdSwIAseTxR

Ex Output:
uYBBdSwIA


Ex Input:
lVlYxTHiNbtFOCArowuoUSsFRI, RndzGibtFOCArowgH

Ex Output:

btFOCArow