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

Ex Input:
jeQzwP, kSQzxq

Ex Output:
Qz


Ex Input:
cvZfWOwa, xOfWOhZs

Ex Output:
fWO


Ex Input:
hVQyfOntBPj, rkJfOntBKmQ

Ex Output:

fOntB