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

Ex Input:
CkZOSZevST, bbZOSZIg

Ex Output:
ZOSZ


Ex Input:
jsXHot, gtXHmB

Ex Output:
XH


Ex Input:
vsWOzdS, GvHWOzeV

Ex Output:

WOz


