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: "distributed bilevel energy allocation mechanism with grid constraints and hidden user information"
  Abstract: A novel distributed energy allocation mechanism for distribution system operator (DSO) market through a bilevel iterative auction is proposed. With the locational marginal price known at the substation node, the DSO runs an upper level auction with aggregators as intermediate agents competing for energy. This DSO level auction takes into account physical grid constraints such as line flows, transformer capacities, and node voltage limits. This auction mechanism is a straightforward implementation of projected gradient descent on the social welfare of all home level agents. Aggregators, which serve home level agents—both buyers and sellers, implement lower level auctions in parallel, through proportional allocation of power, until market equilibrium is established. This is accomplished without asking for the agents’ utility functions and generation capacities that are considered private information. The overall bilevel auction is shown to be globally efficient and weakly budget balanced.

Connected through hyperedge HE-1 (induced by source paper "distribution lmp based transactive day ahead market with variable renewable generation"):
  with members:
    - "prioritizing consumers in smart grid a game theoretic approach"

Connected through hyperedge HE-2 (induced by source paper "pareto optimal allocation of transactive energy at market equilibrium in distribution systems a constrained vector optimization approach"):
  with members:
    - "multi task learning as multi objective optimization"

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.SY(Systems and Control)