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: "regular separability of well structured transition systems"
  Abstract: We investigate languages recognized by well structured transition systems (WSTS) with upward (resp. downward) compatibility. We show that under mild assumptions every two disjoint WSTS languages are regular separable, i.e., there exists a regular language containing one of them and disjoint from the other. In particular, if a language, as well as its complement, are both recognized by a WSTS, then they are necessarily regular.

Connected through hyperedge HE-1 (induced by source paper "regular separability of one counter automata"):
  with members:
    - "separating regular languages with first order logic"
    - "regular separability of parikh automata"
    - "separability of reachability sets of vector addition systems"
    - "invisible pushdown languages"
    - "reachability in two dimensional vector addition systems with states is pspace complete"
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "reachability in two clock timed automata is pspace complete"
    - "separating regular languages by piecewise testable and unambiguous languages"

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)