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

Ex Input:
CUxfOt, dyxfNp

Ex Output:
xf


Ex Input:
njzfcapS, JDzfcYQh

Ex Output:
zfc


Ex Input:
OwrBrPHvFMoM, RcrPHvMkx

Ex Output:

rPHv