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

Ex Input:
dsngGP, KvnglB

Ex Output:
ng


Ex Input:
rCFrfkmXbSHK, mztfkmXwez

Ex Output:
fkmX


Ex Input:
XjbqaKV, BZsbqajS

Ex Output:

bqa


