instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
QqtCFzXHPNFXx, XECFzXHPSGwUuk
answer:
CFzXHP


question:
AeYjeKwZQillzpD, SnqviKwZQillrxuTB
answer:
KwZQill


question:
AVJRwyYPR, HdCRwyGt
answer:

Rwy