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: "improved hardness of approximation for stackelberg shortest path pricing"
  Abstract: We consider the Stackelberg shortest-path pricing problem, which is defined as follows. Given a graph G with fixed-cost and pricable edges and two distinct vertices s and t, we may assign prices to the pricable edges. Based on the predefined fixed costs and our prices, a customer purchases a cheapest s-t-path in G and we receive payment equal to the sum of prices of pricable edges belonging to the path. Our goal is to find prices maximizing the payment received from the customer. While Stackelberg shortest-path pricing was known to be APX-hard before, we provide the first explicit approximation threshold and prove hardness of approximation within 2-o(1).

Connected through hyperedge HE-1 (induced by source paper "negative prices in network pricing games"):
  with members:
    - "toll caps in privatized road networks"
    - "inefficiencies in network models a graph theoretic perspective"
    - "approximate revenue maximization with multiple items"
    - "matroids are immune to braess paradox"
    - "new complexity results and algorithms for the minimum tollbooth problem"
    - "stackelberg shortest path tree game revisited"
    - "the stackelberg minimum spanning tree game"
    - "stackelberg network pricing is hard to approximate"

Connected through hyperedge HE-2 (induced by source paper "specializations and generalizations of the stackelberg minimum spanning tree game"):
  with members:
    - "the stackelberg minimum spanning tree game on planar and bounded treewidth graphs"
    - "the stackelberg minimum spanning tree game"
    - "stackelberg network pricing is hard to approximate"
    - "stackelberg network pricing games"

Connected through hyperedge HE-3 (induced by source paper "the stackelberg minimum spanning tree game on planar and bounded treewidth graphs"):
  with members:
    - "specializations and generalizations of the stackelberg minimum spanning tree game"
    - "the stackelberg minimum spanning tree game"
    - "stackelberg network pricing games"
    - "an approximation algorithm for stackelberg network pricing"

Connected through hyperedge HE-4 (induced by source paper "stackelberg shortest path tree game revisited"):
  with members:
    - "the stackelberg minimum spanning tree game"
    - "stackelberg network pricing is hard to approximate"
    - "stackelberg network pricing games"

Connected through hyperedge HE-5 (induced by source paper "stackelberg pricing is hard to approximate within 2 epsilon"):
  with members:
    - "the stackelberg minimum spanning tree game on planar and bounded treewidth graphs"
    - "the stackelberg minimum spanning tree game"
    - "stackelberg network pricing is hard to approximate"
    - "stackelberg network pricing games"

Connected through hyperedge HE-6 (induced by source paper "stackelberg network pricing games"):
  with members:
    - "the stackelberg minimum spanning tree game on planar and bounded treewidth graphs"
    - "the stackelberg minimum spanning tree game"
    - "algorithmic pricing via virtual valuations"

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.DS(Data Structures and Algorithms)