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

Ex Input:
feYKRk, PrYKMW

Ex Output:
YK


Ex Input:
oXZmCSdFrMumlZcP, eFpOZmCSdFrIuHeS

Ex Output:
ZmCSdFr


Ex Input:
kELaCKnaFhM, PvePLaCKnaKxeB

Ex Output:

LaCKna