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: "on the definition of a theoretical concept of an operating system"
  Abstract: We dwell on how a definition of a theoretical concept of an operating system, suitable to be incorporated in a mathematical theory of operating systems, could look like. This is considered a valuable preparation for the development of a mathematical theory of operating systems.

Connected through hyperedge HE-1 (induced by source paper "bitcoin and beyond exclusively informational money"):
  with members:
    - "practical aspects of the bitcoin system"
    - "the unreasonable fundamental incertitudes behind bitcoin mining"
    - "informaticology combining computer science data science and fiction science"
    - "formaleuros formalcoins and virtual monies"
    - "searching publications on operating systems"
    - "machine structure oriented control code logic"
    - "a static theory of promises"

Connected through hyperedge HE-2 (induced by source paper "formaleuros formalcoins and virtual monies"):
  with members:
    - "searching publications on operating systems"
    - "an interface group for process components"
    - "machine structure oriented control code logic"
    - "tuplix calculus specifications of financial transfer networks"
    - "a static theory of promises"
    - "interface groups and financial transfer architectures"

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.OS(Operating Systems)