instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
KJswoapnXz, EQswoaFyH
answer:
swoa


question:
CiElmOvTqJGVJkfSaDRzE, EjDJwMyxTvTqJGVJkfluB
answer:
vTqJGVJkf


question:
UFRpgXNhQixVbP, kkHRpgXNhwVKzW
answer:

RpgXNh