instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
vSFxjd, AHFxpi
answer:
Fx


question:
CiElmOvTqJGVJkfSaDRzE, EjDJwMyxTvTqJGVJkfluB
answer:
vTqJGVJkf


question:
oKKMwndgNiEGjVc, iQndgNiEGLXWzYH
answer:

ndgNiEG