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

Ex Input:
ykDpbd, YFDpmO

Ex Output:
Dp


Ex Input:
GBTHKtWUzK, ovVNKtWUmVJF

Ex Output:
KtWU


Ex Input:
GurwBBLd, VtrwBnJ

Ex Output:

rwB