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: "bipartite envy free matching"
  Abstract: Bipartite Envy-Free Matching (BEFM) is a relaxation of perfect matching. In a bipartite graph with parts X and Y, a BEFM is a matching of some vertices in X to some vertices in Y, such that each unmatched vertex in X is not adjacent to any matched vertex in Y (so the unmatched vertices do not "envy" the matched ones). The empty matching is always a BEFM. This paper presents sufficient and necessary conditions for the existence of a non-empty BEFM. These conditions are based on cardinality of neighbor-sets, similarly to Hall's condition for the existence of a perfect matching. The conditions can be verified in polynomial time, and in case they are satisfied, a non-empty BEFM can be found by a polynomial-time algorithm. The paper presents some applications of BEFM as a subroutine in fair division algorithms.

Connected through hyperedge HE-1 (induced by source paper "envy freeness in house allocation problems"):
  with members:
    - "approximation algorithms for computing maximin share allocations"

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)