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: "untangling planar graphs from a specified vertex position hard cases"
  Abstract: Given a planar graph G, we consider drawings of G in the plane where edges are represented by straight line segments (which possibly intersect). Such a drawing is specified by an injective embedding @p of the vertex set of G into the plane. Let fix(G,@p) be the maximum integer k such that there exists a crossing-free redrawing @p^' of G which keeps k vertices fixed, i.e., there exist k vertices v"1,...,v"k of G such that @p(v"i)[email protected]^'(v"i) for i=1,...,k. Given a set of points X, let fix^X(G) denote the value of fix(G,@p) minimized over @p locating the vertices of G on X. The absolute minimum of fix(G,@p) is denoted by fix(G). For the wheel graph W"n, we prove that fix^X(W"n)@?(2+o(1))n for every X. With a somewhat worse constant factor this is also true for the fan graph F"n. We inspect also other graphs for which it is known that fix(G)=O(n). We also show that the minimum value fix(G) of the parameter fix^X(G) is always attainable by a collinear X.

Connected through hyperedge HE-1 (induced by source paper "drawing planar graphs with many collinear vertices"):
  with members:
    - "the utility of untangling"
    - "a note on planar partial 3 trees"
    - "untangling polygons and graphs"
    - "untangling a planar graph"
    - "a polynomial bound for untangling geometric planar graphs"
    - "on collinear sets in straight line drawings"

Connected through hyperedge HE-2 (induced by source paper "the utility of untangling"):
  with members:
    - "superpatterns and universal point sets"
    - "sefe with no mapping via large induced outerplane graphs in plane graphs"
    - "how many vertex locations can be arbitrarily chosen when drawing planar graphs"
    - "on universal point sets for planar graphs"
    - "simultaneous embedding of planar graphs"
    - "untangling polygons and graphs"
    - "on a tree and a path with no geometric simultaneous embedding"
    - "untangling a planar graph"

Connected through hyperedge HE-3 (induced by source paper "on collinear sets in straight line drawings"):
  with members:
    - "untangling polygons and graphs"
    - "untangling a planar graph"
    - "a polynomial bound for untangling geometric planar graphs"
    - "on the obfuscation complexity of planar graphs"

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)