using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<double> duplList = new List<double> {1.1, 2.2, 2.2, 3.3, 4.4, 5.5, 5.5, 6.6, 7.7};

        Console.WriteLine(" ");

        for (int i = 0; i < duplList.Count; i++) 

        {

            Console.WriteLine("DuplList List Items indices: " + i + " DuplList List Items: " + duplList[i]);

        }

        for (int i = 0 ; i < duplList.Count -1 ; i++)

        {       

            double st1  = duplList[i+1];

            double nd2  = duplList[i];

​

            if (st1 == nd2)

            {

                duplList.Remove(st1);

            }

        }

        Console.WriteLine(" ");

        for (int i = 0; i < duplList.Count; i++) 

        {

            Console.WriteLine("DeDuplList List Items indices: " + i + " DeDuplList List Items: " + duplList[i]);

        }

        List<double> avgshortList = new List<double>();

        for (int i = duplList.Count - 6; i < duplList.Count; i++) 

        {

            avgshortList.Add(duplList[i]);

        }

​

        double avg = avgshortList.Count > 0 ? 

            Queryable.Average(avgshortList.AsQueryable()) 

            : double.NaN;

        Console.WriteLine(" ");

​

        Console.WriteLine("Latest 6 List's items Average number \n ((7.7 + 6.6 + 5.5 + 4.4 + 3.3 + 2.2) / 6)  = " 

                          + avg.ToString("N2") );

    }

}