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: "robust recoverable and two stage selection problems"
  Abstract: In this paper the following selection problem is discussed. A set of $n$ items is given and we wish to choose a subset of exactly $p$ items of the minimum total cost. This problem is a special case of 0-1 knapsack in which all the item weights are equal to~1. Its deterministic version has a trivial $O(n)$-time algorithm, which consists in choosing $p$ items of the smallest costs. In this paper it is assumed that the item costs are uncertain. Two robust models, namely two-stage and recoverable ones, under discrete and interval uncertainty representations, are discussed. Several positive and negative complexity results for both of them are provided.

Connected through hyperedge HE-1 (induced by source paper "robust two stage combinatorial optimization problems under convex uncertainty"):
  with members:
    - "two stage combinatorial optimization problems under risk"
    - "approximability of the robust representatives selection problem"
    - "robust optimization with incremental recourse"
    - "on the approximability of minmax regret network optimization problems"

Connected through hyperedge HE-2 (induced by source paper "two stage combinatorial optimization problems under risk"):
  with members:
    - "risk averse single machine scheduling complexity and approximation"
    - "approximability of the robust representatives selection problem"

Connected through hyperedge HE-3 (induced by source paper "robust recoverable 0 1 optimization problems under polyhedral uncertainty"):
  with members:
    - "recoverable robust spanning tree problem under interval uncertainty representations"
    - "robust optimization with incremental recourse"

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)