instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
mJoHBJehHtkFS, ZMrDxHBJehHtxS
answer:
HBJehHt


question:
IKrQfT, crrQRg
answer:
rQ


question:
dQILZo, ZrILvL
answer:

IL