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

Ex Input:
HhBhJMpxpty, MxTJMpxnQEf

Ex Output:
JMpx


Ex Input:
UiaECWZf, gRyaECWLGRl

Ex Output:
aECW


Ex Input:
IjRFsnoq, YnERFsVKI

Ex Output:

RFs