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: "on average and highest number of flips in pancake sorting"
  Abstract: We are given a stack of pancakes of different sizes and the only allowed operation is to take several pancakes from the top and flip them. The unburnt version requires the pancakes to be sorted by their sizes at the end, while in the burnt version they additionally need to be oriented burnt-side down. We are interested in the largest value of the number of flips needed to sort a stack of n pancakes, both in the unburnt version (f(n)) and in the burnt version (g(n)). We present exact values of f(n) up to n=19 and of g(n) up to n=17 and disprove a conjecture of Cohen and Blum by showing that the burnt stack -I"1"5 is not the hardest to sort for n=15. We also show that sorting a random stack of n unburnt pancakes can be done with at most 17n/12+O(1) flips on average. The average number of flips of the optimal algorithm for sorting stacks of n burnt pancakes is shown to be between [email protected](n/logn) and 7n/4+O(1) and we conjecture that it is [email protected](n/logn). Finally we show that sorting the stack -I"n needs at least @?(3n+3)/[email protected]? flips, which slightly increases the lower bound on g(n). This bound together with the upper bound for sorting -I"n found by Heydari and Sudborough in 1997 [10] gives the exact number of flips to sort it for n=3(mod4) and n>=15.

Connected through hyperedge HE-1 (induced by source paper "on the number of pancake stacks requiring four flips to be sorted"):
  with members:
    - "cycles in the burnt pancake graphs"
    - "pancake flipping is hard"

Connected through hyperedge HE-2 (induced by source paper "cycles in the burnt pancake graphs"):
  with members:
    - "pancake flipping is hard"

Connected through hyperedge HE-3 (induced by source paper "pancake flipping is hard"):
  with members:
    - "polynomial time sortable stacks of burnt pancakes"

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)