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: "two polynomial algorithms for special maximum matching constructing in trees"
  Abstract: For an arbitrary tree we investigate the problems of constructing a maximum matching which minimizes or maximizes the cardinality of a maximum matching of the graph obtained from original one by its removal and present corresponding polynomial algorithms.

Connected through hyperedge HE-1 (induced by source paper "on upper bounds for parameters related to the construction of special maximum matchings"):
  with members:
    - "on complexity of special maximum matchings constructing"

Connected through hyperedge HE-2 (induced by source paper "characterization of a class of graphs related to pairs of disjoint matchings"):
  with members:
    - "on complexity of special maximum matchings constructing"
    - "note on edge disjoint pairs of matchings"
    - "a note on minimal matching covered graphs"
    - "on trees with a maximum proper partial 0 1 coloring containing a maximum matching"

Connected through hyperedge HE-3 (induced by source paper "on a constructive characterization of a class of trees related to pairs of disjoint matchings"):
  with members:
    - "characterization of a class of graphs related to pairs of disjoint matchings"
    - "on complexity of special maximum matchings constructing"
    - "note on edge disjoint pairs of matchings"
    - "a note on minimal matching covered graphs"
    - "on trees with a maximum proper partial 0 1 coloring containing a maximum matching"

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)