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: "interval colorings of complete bipartite graphs and trees"
  Abstract: A translation from Russian of the work of R.R. Kamalian "Interval colorings of complete bipartite graphs and trees", Preprint of the Computing Centre of the Academy of Sciences of Armenia, Yerevan, 1989. (Was published by the decision of the Academic Council of the Computing Centre of the Academy of Sciences of Armenian SSR and Yerevan State University from 7.09.1989).

Connected through hyperedge HE-1 (induced by source paper "on interval edge colorings of bipartite graphs"):
  with members:
    - "interval colorings of edges of a multigraph"
    - "practical graph isomorphism ii"

Connected through hyperedge HE-2 (induced by source paper "interval edge colorings of complete graphs"):
  with members:
    - "interval colorings of edges of a multigraph"
    - "a note on interval edge colorings of graphs"
    - "interval edge colorings of mobius ladders"

Connected through hyperedge HE-3 (induced by source paper "on cyclically interval edge colorings of trees"):
  with members:
    - "interval edge colorings of mobius ladders"

Connected through hyperedge HE-4 (induced by source paper "a note on upper bounds for the maximum span in interval edge colorings of graphs"):
  with members:
    - "interval edge colorings of some products of 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)