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

Q: GBTHKtWUzK, ovVNKtWUmVJF

A: KtWU
****
Q: wbdHVigIkjNkuAmbr, iSgIkjNkQYyn

A: gIkjNk
****
Q: AHBjFG, EJBjYg

A:
Bj
****