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:
mXHhaCEIwqwEZcz, JZPXbYHhaCEIwZmna
answer:
HhaCEIw


question:
rVxClE, eSxCCz
answer:

xC