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: "generalized gray codes with prescribed ends"
  Abstract: Abstract   An n-bit Gray code is a sequence of all n-bit vectors such that consecutive vectors differ in a single bit. It is well-known that given    α  ,  β  ∈    {  0  ,  1  }    n     , an n-bit Gray code between α and β exists iff the Hamming distance    d  (  α  ,  β  )    of α and β is odd. We generalize this classical result to k pairwise disjoint pairs      α    i    ,    β    i    ∈    {  0  ,  1  }    n     : if    d  (    α    i    ,    β    i    )    is odd for all i and    k    n   , then the set of all n-bit vectors can be partitioned into k sequences such that the i-th sequence leads from      α    i      to      β    i      and consecutive vectors differ in a single bit. This holds for every    n  >  1    with one exception in the case when    n  =  k  +  1  =  4   . Our result is optimal in the sense that for every    n  >  2    there are n pairwise disjoint pairs      α    i    ,    β    i    ∈    {  0  ,  1  }    n      with    d  (    α    i    ,    β    i    )    odd for which such sequences do not exist.

Connected through hyperedge HE-1 (induced by source paper "optimal quasi gray codes does the alphabet matter"):
  with members:
    - "a linear lower bound for incrementing a space optimal integer representation in the bit probe model"
    - "a constant time algorithm for middle levels gray codes"
    - "loopless gray code enumeration and the tower of bucharest"
    - "efficient computation of middle levels gray codes"
    - "snake in the box codes for rank modulation"
    - "improved methods for generating quasi gray codes"

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.DM(Discrete Mathematics)