instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
KfjqnJLciTXqkJK, yqfRcfqnJLcisSB
answer:
qnJLci


question:
wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
answer:
caiUPH


question:
FaLtuBqE, kgLtuJRX
answer:

Ltu