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: "on triangulating k outerplanar graphs"
  Abstract: A k-outerplanar graph is a graph that can be drawn in the plane without crossing such that after k-fold removal of the vertices on the outer-face there are no vertices left. In this paper, we study how to triangulate a k-outerplanar graph while keeping its outerplanarity small. Specifically, we show that not all k-outerplanar graphs can be triangulated so that the result is k-outerplanar, but they can be triangulated so that the result is (k+1)-outerplanar.

Connected through hyperedge HE-1 (induced by source paper "detecting and counting small patterns in planar graphs in subexponential parameterized time"):
  with members:
    - "homomorphisms are a good basis for counting small subgraphs"
    - "computing the number of induced copies of a fixed graph in a bounded degree graph"
    - "subexponential parameterized algorithms for planar and apex minor free graphs via low treewidth pattern covering"
    - "counting matchings with k unmatched vertices in planar graphs"
    - "approximating the partition function of planar two state spin systems"
    - "approximate counting via correlation decay on planar graphs"
    - "beyond bidimensionality parameterized subexponential algorithms on directed graphs"
    - "planar subgraph isomorphism revisited"

Connected through hyperedge HE-2 (induced by source paper "pixel and voxel representations of graphs"):
  with members:
    - "1 visibility representations of 1 planar graphs"
    - "bar 1 visibility graphs and their relation to other nearly planar graphs"
    - "equilateral l contact graphs"
    - "computing cartograms with optimal complexity"
    - "optimal polygonal representation of planar graphs"
    - "rectangular layouts and contact graphs"

Connected through hyperedge HE-3 (induced by source paper "separating an r outerplanar graph into gluable pieces"):
  with members:
    - "optimal parameterized algorithms for planar facility location problems using voronoi diagrams"
    - "explicit linear kernels via dynamic programming"

Connected through hyperedge HE-4 (induced by source paper "triangulating planar graphs while keeping the pathwidth small"):
  with members:
    - "2 connecting outerplanar graphs without blowing up the pathwidth"

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.DM(Discrete Mathematics)