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: "reachability problem for weak multi pushdown automata"
  Abstract: This paper is about reachability analysis in a restricted subclass of#N#multi-pushdown automata. We assume that the control states of an automaton are#N#partially ordered, and all transitions of an automaton go downwards with#N#respect to the order. We prove decidability of the reachability problem, and#N#computability of the backward reachability set. As the main contribution, we#N#identify relevant subclasses where the reachability problem becomes#N#NP-complete. This matches the complexity of the same problem for#N#communication-free vector addition systems, a special case of stateless#N#multi-pushdown automata.

Connected through hyperedge HE-1 (induced by source paper "analyzing timed systems using tree automata"):
  with members:
    - "timed pushdown automata revisited"
    - "model checking of ordered multi pushdown automata"

Connected through hyperedge HE-2 (induced by source paper "reachability analysis of first order definable pushdown systems"):
  with members:
    - "timed pushdown automata revisited"
    - "automata theory in nominal sets"
    - "saturation algorithms for model checking pushdown systems"
    - "model checking of ordered multi pushdown automata"
    - "ltl with the freeze quantifier and register automata"
    - "alternating timed automata"

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.LO(Logic in Computer Science)