instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
kyADtWLlnmYv, tcaKvDtWLlnvBq
answer:
DtWLln


question:
wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
answer:
caiUPH


question:
rKdWMfPTy, rLuZdWMflQ
answer:

dWMf