instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
HKqfdEvqDuGhWByFlzIEeYh, VVaZfkLCMuGhWByFlzIOZaXbMCA
answer:
uGhWByFlzI


question:
wYhGWdRC, cFGWdHEy
answer:
GWd


question:
BYMJQzqftq, GUWoQzqffX
answer:

Qzqf