instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
hGyDyQYdxCCuD, BQiFOyQYdxel
answer:
yQYdx


question:
oXZmCSdFrMumlZcP, eFpOZmCSdFrIuHeS
answer:
ZmCSdFr


question:
AVWYFumjgdSabJr, VXumjgdSaVmCWR
answer:

umjgdSa