instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
PzXzvmYrlGZgOBk, iKnzvmYrlGZgOrs
answer:
zvmYrlGZgO


question:
OUNqomxFcLXhWdfB, gdqomxFcLHQPCu
answer:
qomxFcL


question:
XznNQmnH, kdkMnNQmPwW
answer:

nNQm