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

Q: OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO

A: QQnzOF
****
Q: ezVsFayUPcrte, lfsFayUMPTqx

A: sFayU
****
Q: jTGIYBIIO, vnrtGIYBjOMp

A:
GIYB
****