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

Q: jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ

A: mecfxMc
****
Q: jXbgnl, lUbglP

A: bg
****
Q: vSFxjd, AHFxpi

A:
Fx
****