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: "better s t tours by gao trees"
  Abstract: We consider the $s$-$t$-path TSP: given a finite metric space with two elements $s$ and $t$, we look for a path from $s$ to $t$ that contains all the elements and has minimum total distance. We improve the approximation ratio for this problem from 1.599 to 1.566. Like previous algorithms, we solve the natural LP relaxation and represent an optimum solution $x^*$ as a convex combination of spanning trees. Gao showed that there exists a spanning tree in the support of $x^*$ that has only one edge in each narrow cut (i.e., each cut $C$ with $x^*(C)<2$). Our main theorem says that the spanning trees in the convex combination can be chosen such that many of them are such "Gao trees''.

Connected through hyperedge HE-1 (induced by source paper "reducing path tsp to tsp"):
  with members:
    - "beating the integrality ratio for s t tours in graphs"
    - "a 1 5 approximation for path tsp"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"
    - "new inapproximability bounds for tsp"
    - "approximating minimum cost connected t joins"
    - "improving christofides algorithm for the s t path tsp"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-2 (induced by source paper "an improved upper bound on the integrality ratio for the s t path tsp"):
  with members:
    - "a 1 5 approximation for path tsp"
    - "layers and matroids for the traveling salesman s paths"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-3 (induced by source paper "a 1 5 approximation for path tsp"):
  with members:
    - "reassembling trees for the traveling salesman"
    - "on the metric s t path traveling salesman problem"
    - "13 9 approximation for graphic tsp"
    - "minimum cuts in near linear time"

Connected through hyperedge HE-4 (induced by source paper "approaching frac 3 2 for the s t path tsp"):
  with members:
    - "a 1 5 approximation for path tsp"
    - "an improved upper bound on the integrality ratio for the s t path tsp"
    - "layers and matroids for the traveling salesman s paths"
    - "reassembling trees for the traveling salesman"
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-5 (induced by source paper "layers and matroids for the traveling salesman s paths"):
  with members:
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-6 (induced by source paper "the salesman s improved paths 3 2 1 34 integrality gap and approximation ratio"):
  with members:
    - "reassembling trees for the traveling salesman"
    - "on the metric s t path traveling salesman problem"
    - "approximating minimum cost connected t joins"

Connected through hyperedge HE-7 (induced by source paper "reassembling trees for the traveling salesman"):
  with members:
    - "an experimental evaluation of the best of many christofides algorithm for the traveling salesman problem"
    - "on the metric s t path traveling salesman problem"
    - "eight fifth approximation for the path tsp"
    - "approximating minimum cost connected t joins"
    - "improving christofides algorithm for the s t path tsp"
    - "approximating graphic tsp by matchings"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-8 (induced by source paper "an experimental evaluation of the best of many christofides algorithm for the traveling salesman problem"):
  with members:
    - "reassembling trees for the traveling salesman"
    - "on the metric s t path traveling salesman problem"
    - "eight fifth approximation for the path tsp"
    - "improving christofides algorithm for the s t path tsp"
    - "approximating graphic tsp by matchings"
    - "13 9 approximation for graphic tsp"

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)