human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "submodularity on a tree unifying l natural convex and bisubmodular functions"):
  Abstract: We introduce a new class of functions that can be minimized in polynomial time in the value oracle model. These are functions $f$ satisfying $f(x)+f(y)\ge f(x \sqcap y)+f(x \sqcup y)$ where the domain of each variable $x_i$ corresponds to nodes of a rooted binary tree, and operations $\sqcap,\sqcup$ are defined with respect to this tree. Special cases include previously studied $L^\natural$-convex and bisubmodular functions, which can be obtained with particular choices of trees. We present a polynomial-time algorithm for minimizing functions in the new class. It combines Murota's steepest descent algorithm for $L^\natural$-convex functions with bisubmodular minimization algorithms.

Includes members:
  Member "min csp on four elements moving beyond submodularity":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "piecewise linear valued csps solvable by linear programming relaxation")
  Member "generalising tractable vcsps defined by symmetric tournament pair multimorphisms":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "hybrid tractability of valued constraint problems")
  Member "a dichotomy theorem for conservative general valued csps":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "min csp on four elements moving beyond submodularity")
  Member "the complexity of conservative finite valued csps":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "min csp on four elements moving beyond submodularity")
  Member "on the complexity of submodular function minimisation on diamonds":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "combinatorial optimization algorithms via polymorphisms")

Question: Please tell me which class the source paper 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)