instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
OyrqfQQnzOFUzrkDM, iBkQQnzOFewhjvO
answer:
QQnzOF


question:
UvYbfKFybXofcwLRrLRiK, BgMZKFybXofcVe
answer:
KFybXofc


question:
mwRepDofqYUTPB, xysscpDofqck
answer:

pDofq