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: "the k in a tree problem for graphs of girth at least k"
  Abstract: For all integers k>=3, we give an O(n^4)-time algorithm for the problem whose instance is a graph G of girth at least k together with k vertices and whose question is ''Does G contains an induced subgraph containing the k vertices and isomorphic to a tree?''. This directly follows for k=3 from the three-in-a-tree algorithm of Chudnovsky and Seymour and for k=4 from a result of Derhy, Picouleau and Trotignon. Here we solve the problem for k>=5. Our algorithm relies on a structural description of graphs of girth at least k that do not contain an induced tree covering k given vertices (k>=5).

Connected through hyperedge HE-1 (induced by source paper "three in a tree in near linear time"):
  with members:
    - "graph pattern detection hardness for all induced patterns and faster non induced cycles"
    - "a faster algorithm to recognize even hole free graphs"
    - "on the structure of pan even hole free graphs"
    - "powers of tensors and fast matrix multiplication"
    - "detecting an induced net subdivision"
    - "large induced subgraphs via triangulations and cmso"
    - "induced disjoint paths in claw free graphs"
    - "detecting 2 joins faster"

Connected through hyperedge HE-2 (induced by source paper "induced disjoint paths in claw free graphs"):
  with members:
    - "the k in a path problem for claw free graphs"
    - "domination when the stars are out"
    - "finding topological subgraphs is fixed parameter tractable"
    - "detecting induced subgraphs"
    - "the four in a tree problem in triangle free graphs"

Connected through hyperedge HE-3 (induced by source paper "the k in a path problem for claw free graphs"):
  with members:
    - "detecting induced subgraphs"
    - "the four in a tree problem in triangle free 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)