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

jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ
mecfxMc

jXqEDHTCxTiUAICWZJdpmYq, GBTCxTiUAICZKnLgZBXi
TCxTiUAIC

IVnbnqBqdPcXfHotUzCYoaGQy, PAlyypBRRBqdPcXfHotpZs

BqdPcXfHot