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: "online trading as a secretary problem"
  Abstract: We consider the online problem in which an intermediary trades identical items with a sequence of n buyers and n sellers, each of unit demand. We assume that the values of the traders are selected by an adversary and the sequence is randomly permuted. We give competitive algorithms for two objectives: welfare and gain-from-trade.

Connected through hyperedge HE-1 (induced by source paper "efficient two sided markets with limited information"):
  with members:
    - "optimal single choice prophet inequalities from samples"
    - "bulow klemperer style results for welfare maximization in two sided markets"
    - "improved truthful mechanisms for combinatorial auctions with submodular bidders"
    - "the best of both worlds asymptotically efficient mechanisms with a guarantee on the expected gains from trade"
    - "approximating gains from trade in two sided markets via simple mechanisms"
    - "fixed price approximability of the optimal gain from trade"
    - "online market intermediation"
    - "sbba a strongly budget balanced double auction mechanism"

Connected through hyperedge HE-2 (induced by source paper "how to hire secretaries with stochastic departures"):
  with members:
    - "packing returning secretaries"
    - "improved approximations for free order prophets and second price auctions"
    - "prophet secretary surpassing the 1 1 e barrier"
    - "prophet secretary for combinatorial auctions and matroids"
    - "beyond matroids secretary problem and prophet inequality with general constraints"
    - "o log log rank competitive ratio for the matroid secretary problem"
    - "matroid prophet inequalities"

Connected through hyperedge HE-3 (induced by source paper "multi unit bilateral trade"):
  with members:
    - "approximating gains from trade in two sided markets via simple mechanisms"
    - "fixed price approximability of the optimal gain from trade"
    - "muda a truthful multi unit double auction mechanism"
    - "online market intermediation"
    - "almost efficient mechanisms for bilateral trading"
    - "online truthful mechanisms for multi sided markets"
    - "simple and near optimal mechanisms for market intermediation"

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.GT(Computer Science and Game Theory)