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: "the reachability problem for vector addition systems with a stack is not elementary"
  Abstract: By adapting the iterative yardstick construction of Stockmeyer, we show that the reachability problem for vector addition systems with a stack does not have elementary complexity. As a corollary, the same lower bound holds for the satisfiability problem for a two-variable first-order logic on trees in which unbounded data may label only leaf nodes. Whether the two problems are decidable remains an open question.

Connected through hyperedge HE-1 (induced by source paper "on functions weakly computable by pushdown petri nets and related systems"):
  with members:
    - "reachability in vector addition systems is primitive recursive in fixed dimension"
    - "the reachability problem for petri nets is not elementary"
    - "reasoning about data repetitions with counter systems"
    - "complexity hierarchies beyond elementary"
    - "on boundedness problems for pushdown vector addition systems"
    - "on the coverability problem for pushdown vector addition systems in one dimension"
    - "the power of priority channel systems"
    - "approximating petri net reachability along context free traces"

Connected through hyperedge HE-2 (induced by source paper "coverability is undecidable in one dimensional pushdown vector addition systems with resets"):
  with members:
    - "the emptiness problem for valence automata over graph monoids"
    - "reachability in two dimensional unary vector addition systems with states is nl complete"
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "on the coverability problem for pushdown vector addition systems in one dimension"
    - "approximating petri net reachability along context free traces"

Connected through hyperedge HE-3 (induced by source paper "demystifying reachability in vector addition systems"):
  with members:
    - "reasoning about data repetitions with counter systems"
    - "complexity hierarchies beyond elementary"
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "an approach to computing downward closures"
    - "complexity bounds for ordinal based termination"
    - "algorithmic verification of asynchronous programs"
    - "ackermannian and primitive recursive bounds with dickson s lemma"
    - "on selective unboundedness of vass"

Connected through hyperedge HE-4 (induced by source paper "on boundedness problems for pushdown vector addition systems"):
  with members:
    - "demystifying reachability in vector addition systems"
    - "on the coverability problem for pushdown vector addition systems in one dimension"
    - "reachability in two clock timed automata is pspace complete"

Connected through hyperedge HE-5 (induced by source paper "on the coverability problem for pushdown vector addition systems in one dimension"):
  with members:
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "algorithmic verification of asynchronous programs"
    - "approximating petri net reachability along context free traces"

Connected through hyperedge HE-6 (induced by source paper "interprocedural reachability for flat integer programs"):
  with members:
    - "underapproximation of procedure summaries for integer programs"
    - "safety problems are np complete for flat integer programs with octagonal loops"
    - "taming past ltl and flat counter systems"
    - "an extension of parikh s theorem beyond idempotence"
    - "approximating petri net reachability along context free traces"
    - "the octagon abstract domain"

Connected through hyperedge HE-7 (induced by source paper "decidable models of recursive asynchronous concurrency"):
  with members:
    - "complexity hierarchies beyond elementary"
    - "reachability analysis of communicating pushdown systems"
    - "queue dispatch asynchronous systems"
    - "on selective unboundedness of vass"

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.FL(Formal Languages and Automata Theory)