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

Ex Input:
spGRUmIYuGl, qkqRUmItqU

Ex Output:
RUmI


Ex Input:
nhGinCtvLartcMPhJwGRbpZNrq, iQJlFKayEartcMPhJwDRROB

Ex Output:
artcMPhJw


Ex Input:
qSZUrF, ovZUct

Ex Output:

ZU