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

Q: EPUxsZtt, KgxsZuXM

A: xsZ
****
Q: VutZiVkDQcVpQO, BDQVDyBdiVkDQcVpuvNN

A: iVkDQcVp
****
Q: sdldNf, uvldla

A:
ld
****