instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
fWJdaAfOCfejXZvidHM, gOpfOCfejXZbtLvSLZI
answer:
fOCfejXZ


question:
ptVlCwpfOZIi, QEdyVlCwpfOwp
answer:
VlCwpfO


question:
HBQpCkvyLs, WUpCkvlm
answer:

pCkv