human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "blockchain technologies for smart energy systems fundamentals challenges and solutions"
  Abstract: In this paper, we discuss the integration of blockchain in smart energy systems. We present various blockchain technology solutions, review important blockchain platforms, and several blockchain based smart energy projects in different smart energy domains. The majority of blockchain platforms with embedded combination of blockchain technology solutions are computing- and resource- intensive, and hence not entirely suitable for smart energy applications. We consider the requirements of smart energy systems and accordingly identify appropriate blockchain technology solutions for smart energy applications. Our analysis can help in the development of flexible blockchain platforms for smart energy systems.

Connected through hyperedge HE-1 (induced by source paper "peer to peer trading in electricity networks an overview"):
  with members:
    - "a motivational game theoretic approach for peer to peer energy trading in the smart grid"
    - "energy crowdsourcing and peer to peer energy trading in blockchain enabled smart grids"
    - "decentralized p2p energy trading under network constraints in a low voltage network"
    - "peer to peer energy trading with sustainable user participation a game theoretic approach"
    - "price discrimination for energy trading in smart grid a game theoretic approach"
    - "prioritizing consumers in smart grid a game theoretic approach"
    - "three party energy management with distributed energy resources in smart grid"

Connected through hyperedge HE-2 (induced by source paper "blockchain for future smart grid a comprehensive survey"):
  with members:
    - "exploring the attack surface of blockchain a systematic overview"
    - "an efficient blockchain based hierarchical authentication mechanism for energy trading in v2g environment"
    - "when energy trading meets blockchain in electrical power system the state of the art"
    - "energy crowdsourcing and peer to peer energy trading in blockchain enabled smart grids"
    - "blockchain based grid operation services for transactive energy systems"
    - "key management systems for smart grid advanced metering infrastructure a survey"
    - "a survey on the security of blockchain systems"
    - "a survey on security and privacy issues of bitcoin"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.CY(Computers and Society)