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

Ex Input:
jLbHvZmecfxMcGLXGVsO, erFBGmecfxMcJtDyKGZ

Ex Output:
mecfxMc


Ex Input:
FiKGCRXutEOzMqP, xdxRXutEsl

Ex Output:
RXutE


Ex Input:
XMABnvhDl, eEBnvhnarD

Ex Output:

Bnvh