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

Ex Input:
cvZfWOwa, xOfWOhZs

Ex Output:
fWO


Ex Input:
cUCQXEFSgRZjK, RYdvUQXEFSgRZVlwx

Ex Output:
QXEFSgRZ


Ex Input:
WRXoBgiUGAivfCrerWclXmJ, gacUGAivfCrerTrVL

Ex Output:

UGAivfCrer