instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jJjsASFfCqVV, AkjsASFfBFwPy
answer:
jsASFf


question:
NNpkdhvgT, BMkAkdhvrwV
answer:
kdhv


question:
wYtdhaQmIkhvxvcTuJvMRJBa, hApIBLKhekhvxvcTuJBLsvWv
answer:

khvxvcTuJ