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

Q: pJqqIW, Ivqqxw

A: qq
****
Q: eMDNXl, ZZDNAa

A: DN
****
Q: alvsJUXpvGqLrp, sOJRfJUXpvGqXTap

A:
JUXpvGq
****