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

Ex Input:
lrBJDRkT, jmBJDrI

Ex Output:
BJD


Ex Input:
njzfcapS, JDzfcYQh

Ex Output:
zfc


Ex Input:
pKzvBtnNLXF, HqvBtnvR

Ex Output:

vBtn