using System;

​

public class Program

{

    string[] topics  = {"operating systems", "Memory Management", "Fetch-Decode-Execute Cycle", "Scheduling", "BIOS", "Virtual machines"};

    string[] ntopics = {"Packets", "TCPIP", "Network Security", "HashTables", "Search Engines", "Compression", "Encryption", "Hardware", "OSI", "Databases", "Boolean Algebra", "Graphs","binary Tree", "Networks", "DataStructures", "ACID", "Normalisation"};

    int x;

    Random rnd = new Random();

    public static void Main()

    {

        Program program = new Program();

        program.ranTopic();

    }

    void ranTopic(){

        x = rnd.Next(0,topics.Length-1);

        Console.WriteLine(ntopics[x]);

    }

}