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

Ex Input:
jsXHot, gtXHmB

Ex Output:
XH


Ex Input:
OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO

Ex Output:
QQnzOF


Ex Input:
HkTMqTuPD, sSaTMqTbbzX

Ex Output:

TMqT