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: "contracting bipartite graphs to paths and cycles"
  Abstract: Testing if a given graph $G$ contains the $k$-vertex path $P_k$ as a minor or as an induced minor is trivial for every fixed integer $k\geq 1$. However, the situation changes for the problem of checking if a graph can be modified into $P_k$ by using only edge contractions. In this case the problem is known to be NP-complete even if $k=4$. This led to an intensive investigation for testing contractibility on restricted graph classes. We focus on bipartite graphs. Heggernes, van 't Hof, L\'{e}v\^{e}que and Paul proved that the problem stays NP-complete for bipartite graphs if $k=6$. We strengthen their result from $k=6$ to $k=5$. We also show that the problem of contracting a bipartite graph to the $6$-vertex cycle $C_6$ is NP-complete. The cyclicity of a graph is the length of the longest cycle the graph can be contracted to. As a consequence of our second result, determining the cyclicity of a bipartite graph is NP-hard.

Connected through hyperedge HE-1 (induced by source paper "contracting to a longest path in h free graphs"):
  with members:
    - "on the parameterized complexity of contraction to generalization of trees"
    - "independent feedback vertex set for p_5 free graphs"
    - "polynomial time algorithms for the longest induced path and induced disjoint paths problems on graphs of bounded mim width"
    - "a faster fpt algorithm for bipartite contraction"
    - "obtaining planarity by contracting few edges"
    - "finding small separators in linear time via treewidth reduction"
    - "contracting graphs to paths and trees"
    - "obtaining a bipartite graph by contracting few edges"

Connected through hyperedge HE-2 (induced by source paper "connected vertex cover for sp_1 p_5 free graphs"):
  with members:
    - "contracting to a longest path in h free graphs"
    - "minimum connected transversals in graphs new hardness results and tractable cases using the price of connectivity"
    - "polynomial time algorithm for maximum weight independent set on p_6 free graphs"
    - "independent feedback vertex set for p_5 free graphs"
    - "maximum weight independent set in lclaw free graphs in polynomial time"
    - "the price of connectivity for vertex cover"

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)