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: "intelliad understanding in app ad costs from users perspective"
  Abstract: Ads are an important revenue source for mobile app development, especially for free apps, whose expense can be compensated by ad revenue. The ad benefits also carry with costs. For example, too many ads can interfere the user experience, leading to less user retention and reduced earnings ultimately. In the paper, we aim at understanding the ad costs from users perspective. We utilize app reviews, which are widely recognized as expressions of user perceptions, to identify the ad costs concerned by users. Four types of ad costs, i.e., number of ads, memory/CPU overhead, traffic usage, and bettery consumption, have been discovered from user reviews. To verify whether different ad integration schemes generate different ad costs, we first obtain the commonly used ad schemes from 104 popular apps, and then design a framework named IntelliAd to automatically measure the ad costs of each scheme. To demonstrate whether these costs indeed influence users reactions, we finally observe the correlations between the measured ad costs and the user perceptions. We discover that the costs related to memory/CPU overhead and battery consumption are more concerned by users, while the traffic usage is less concerned by users in spite of its obvious variations among different schemes in the experiments. Our experimental results provide the developers with suggestions on better incorporating ads into apps and, meanwhile, ensuring the user experience.

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.CY(Computers and Society)