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: "obtaining planarity by contracting few edges"
  Abstract: The Planar Contraction problem is to test whether a given graph can be made planar by using at most k edge contractions. This problem is known to be NP-complete. We show that it is fixed-parameter tractable when parameterized by k.

Connected through hyperedge HE-1 (induced by source paper "hitting topological minor models in planar graphs is fixed parameter tractable"):
  with members:
    - "the planar directed k vertex disjoint paths problem is fixed parameter tractable"
    - "finding topological subgraphs is fixed parameter tractable"
    - "obtaining a planar graph by vertex deletion"

Connected through hyperedge HE-2 (induced by source paper "contracting to a longest path in h free graphs"):
  with members:
    - "on the parameterized complexity of contraction to generalization of trees"
    - "independent feedback vertex set for p_5 free graphs"
    - "contracting bipartite graphs to paths and cycles"
    - "polynomial time algorithms for the longest induced path and induced disjoint paths problems on graphs of bounded mim width"
    - "a faster fpt algorithm for bipartite contraction"
    - "finding small separators in linear time via treewidth reduction"
    - "contracting graphs to paths and trees"
    - "obtaining a bipartite graph by contracting few edges"

Connected through hyperedge HE-3 (induced by source paper "an improved kernel for the cycle contraction problem"):
  with members:
    - "a faster fpt algorithm for bipartite contraction"
    - "contracting graphs to paths and trees"
    - "obtaining a bipartite graph by contracting few edges"

Connected through hyperedge HE-4 (induced by source paper "exact algorithms via monotone local search"):
  with members:
    - "exact algorithms for maximum independent set"
    - "faster algorithms to enumerate hypergraph transversals"
    - "a faster fpt algorithm and a smaller kernel for block graph vertex deletion"
    - "faster exact and parameterized algorithm for feedback vertex set in tournaments"
    - "on feedback vertex set new measure and new structures"
    - "an fpt algorithm and a polynomial kernel for linear rankwidth 1 vertex deletion"
    - "unit interval editing is fixed parameter tractable"
    - "linear recognition of almost interval graphs"

Connected through hyperedge HE-5 (induced by source paper "a faster fpt algorithm for bipartite contraction"):
  with members:
    - "linear time parameterized algorithms via skew symmetric multicuts"
    - "linear time fpt algorithms via network flow"
    - "interval deletion is fixed parameter tractable"
    - "faster parameterized algorithms using linear programming"
    - "on group feedback vertex set parameterized by the size of the cutset"
    - "representative sets and irrelevant vertices new tools for kernelization"
    - "finding small separators in linear time via treewidth reduction"
    - "compression via matroids a randomized polynomial kernel for odd cycle transversal"

Connected through hyperedge HE-6 (induced by source paper "msol restricted contractibility to planar graphs"):
  with members:
    - "obtaining a bipartite graph by contracting few edges"
    - "obtaining a planar graph by vertex deletion"
    - "computing crossing numbers in quadratic time"

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.DS(Data Structures and Algorithms)