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:
sHndIbPaygfNvnquxIHeteW, huLmJWXZIgfNvnquxIViQDhbuoL
answer:
gfNvnquxI


question:
SZvmvtDkUDryuqBzR, tUvtDkUDrBjEZ
answer:

vtDkUDr