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

Q: eMDNXl, ZZDNAa

A: DN
****
Q: oiNEYHxbvAb, bcDDdEYHxbCREd

A: EYHxb
****
Q: PHQctjgVF, rzDQctjzS

A:
Qctj
****