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: "step indexed relational reasoning for countable nondeterminism"
  Abstract: Programming languages with countable nondeterministic choice are#N#computationally interesting since countable nondeterminism arises when modeling#N#fairness for concurrent systems. Because countable choice introduces#N#non-continuous behaviour, it is well-known that developing semantic models for#N#programming languages with countable nondeterminism is challenging. We present#N#a step-indexed logical relations model of a higher-order functional programming#N#language with countable nondeterminism and demonstrate how it can be used to#N#reason about contextually defined may- and must-equivalence. In earlier#N#step-indexed models, the indices have been drawn from {\omega}. Here the#N#step-indexed relations for must-equivalence are indexed over an ordinal greater#N#than {\omega}.

Connected through hyperedge HE-1 (induced by source paper "a higher order logic for concurrent termination preserving refinement"):
  with members:
    - "design and implementation of concurrent c0"

Connected through hyperedge HE-2 (induced by source paper "step indexed logical relations for probability"):
  with members:
    - "logical step indexed logical relations"
    - "probabilistic operational semantics for the lambda calculus"

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)