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: "an improved tight closure algorithm for integer octagonal constraints"
  Abstract: Integer octagonal constraints (a.k.a. ``Unit Two Variables Per Inequality'' or ``UTVPI integer constraints'') constitute an interesting class of constraints for the representation and solution of integer problems in the fields of constraint programming and formal analysis and verification of software and hardware systems, since they couple algorithms having polynomial complexity with a relatively good expressive power. The main algorithms required for the manipulation of such constraints are the satisfiability check and the computation of the inferential closure of a set of constraints. The latter is called `tight' closure to mark the difference with the (incomplete) closure algorithm that does not exploit the integrality of the variables. In this paper we present and fully justify an O(n^3) algorithm to compute the tight closure of a set of UTVPI integer constraints.

Connected through hyperedge HE-1 (induced by source paper "incrementally closing octagons"):
  with members:
    - "incremental satisfiability and implication for utvpi constraints"
    - "the octagon abstract domain"
    - "a static analyzer for large safety critical software"

Connected through hyperedge HE-2 (induced by source paper "deciding conditional termination"):
  with members:
    - "the octagon abstract domain"

Connected through hyperedge HE-3 (induced by source paper "safety problems are np complete for flat integer programs with octagonal loops"):
  with members:
    - "reachability in two dimensional vector addition systems with states is pspace complete"

Connected through hyperedge HE-4 (induced by source paper "ranking functions for linear constraint loops"):
  with members:
    - "ranking function synthesis for linear lasso programs"
    - "deciding conditional termination"
    - "linear ranking for linear lasso programs"
    - "proving termination starting from the end"
    - "eventual linear ranking functions"
    - "monotonicity constraints for termination in the integer domain"
    - "the octagon abstract domain"
    - "the parma polyhedra library toward a complete set of numerical abstractions for the analysis and verification of hardware and software systems"

Connected through hyperedge HE-5 (induced by source paper "exact join detection for convex polyhedra and other numerical abstractions"):
  with members:
    - "a new numerical abstract domain based on difference bound matrices"
    - "applications of polyhedral computations to the analysis and verification of hardware and software systems"
    - "the octagon abstract domain"
    - "the parma polyhedra library toward a complete set of numerical abstractions for the analysis and verification of hardware and software systems"

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)