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

Ex Input:
PQSFjlnU, kTSFjMUh

Ex Output:
SFj


Ex Input:
njzfcapS, JDzfcYQh

Ex Output:
zfc


Ex Input:
ZqBFMTLkMw, bvTZMTLkXoJU

Ex Output:

MTLk