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: "sorting networks the end game"
  Abstract: This paper studies properties of the back end of a sorting network and illustrates the utility of these in the search for networks of optimal size or depth. All previous works focus on properties of the front end of networks and on how to apply these to break symmetries in the search. The new properties help shed understanding on how sorting networks sort and speed-up solvers for both optimal size and depth by an order of magnitude.

Connected through hyperedge HE-1 (induced by source paper "optimal depth sorting networks"):
  with members:
    - "sorting networks to the end and back again"
    - "solving and verifying the boolean pythagorean triples problem via cube and conquer"
    - "new bounds on optimal sorting networks"
    - "computing the ramsey number r 4 3 3 using abstraction and symmetry breaking"
    - "applying sorting networks to synthesize optimized sorting libraries"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"
    - "computer aided proof of erdos discrepancy properties"

Connected through hyperedge HE-2 (induced by source paper "sorting networks to the end and back again"):
  with members:
    - "optimal depth sorting networks"
    - "new bounds on optimal sorting networks"
    - "applying sorting networks to synthesize optimized sorting libraries"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "optimal sorting networks"

Connected through hyperedge HE-3 (induced by source paper "sorting networks the final countdown"):
  with members:
    - "optimal depth sorting networks"
    - "towards optimal sorting networks the third level"
    - "practical algorithms for finding extremal sets"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"

Connected through hyperedge HE-4 (induced by source paper "applying sorting networks to synthesize optimized sorting libraries"):
  with members:
    - "new bounds on optimal sorting networks"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"
    - "optimal sorting networks"

Connected through hyperedge HE-5 (induced by source paper "new bounds on optimal sorting networks"):
  with members:
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "optimal sorting networks"

Connected through hyperedge HE-6 (induced by source paper "towards optimal sorting networks the third level"):
  with members:
    - "optimal depth sorting networks"

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)