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

Ex Input:
mCxQTIaXN, mWQTIaxzPT

Ex Output:
QTIa


Ex Input:
BmwpAnWJ, klVwpAFw

Ex Output:
wpA


Ex Input:
MBRyfDRKyrk, vdbHkfDRKyooGp

Ex Output:

fDRKy