instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
vhZuXCsIkQR, YflCuXCsIkLu
answer:
uXCsIk


question:
LudFxiaqbX, UWMPnFxiaqikiDx
answer:
Fxiaq


question:
KLbwtBhoDgFcqHaAAOM, IpDhrLoshoDgFcqHBlfgs
answer:

hoDgFcqH