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: "symbolic backwards reachability analysis for higher order pushdown systems"
  Abstract: Higher-order pushdown systems (PDSs) generalise pushdown systems through the#N#use of higher-order stacks, that is, a nested "stack of stacks" structure.#N#These systems may be used to model higher-order programs and are closely#N#related to the Caucal hierarchy of infinite graphs and safe higher-order#N#recursion schemes.#N#  We consider the backwards-reachability problem over higher-order Alternating#N#PDSs (APDSs), a generalisation of higher-order PDSs. This builds on and extends#N#previous work on pushdown systems and context-free higher-order processes in a#N#non-trivial manner. In particular, we show that the set of configurations from#N#which a regular set of higher-order APDS configurations is reachable is regular#N#and computable in n-EXPTIME. In fact, the problem is n-EXPTIME-complete.#N#  We show that this work has several applications in the verification of#N#higher-order PDSs, such as linear-time model-checking, alternation-free#N#mu-calculus model-checking and the computation of winning regions of#N#reachability games.

Connected through hyperedge HE-1 (induced by source paper "saturation algorithms for model checking pushdown systems"):
  with members:
    - "saturation of concurrent collapsible pushdown systems"
    - "modeling and verification of infinite systems with resources"
    - "model checking of ordered multi pushdown automata"
    - "symbolic reachability analysis of higher order context free processes"

Connected through hyperedge HE-2 (induced by source paper "reachability in higher order counters"):
  with members:
    - "strictness of the collapsible pushdown hierarchy"
    - "symbolic reachability analysis of higher order context free processes"

Connected through hyperedge HE-3 (induced by source paper "algorithmic metatheorems for decidable ltl model checking over infinite systems"):
  with members:
    - "a framework to handle linear temporal properties in omega regular model checking"
    - "on computing fixpoints in well structured regular model checking with applications to lossy channel systems"

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.CC(Computational Complexity)