using System;

public class Program

{

    public static void Main()

    {

        Forcasting sample = new Forcasting();

    }

}

class Forcasting

{

    private double [] actual;

    private double [] forcast;

    private double alpha;

    private double [] perDev;

    private double  avPerDev;

    public  double [] Actual

    {

        set

        {

        actual = value;

        }

        get

        {

            return actual;

        }

    }

    public  double [] Forcst

    {

        set

        {

        forcast = value;

        }

        get

        {

            return forcast;

        }

    }

    public  double Alpha

    {

        set

        {

        alpha = value;

        }

        get

        {

            return alpha;

        }

    }

    public  double [] PerDev

    {

        get

        {

            return PerDev;

        }

    }

    public  double AvPerDev

    {

        get

        {

            return avPerDev;

        }

    }

    public Forcasting()

    {

         InputData();

         ForcastC();

         PErDev();

         AVDev();

         OutPut();

         Results();

    }

    public void InputData()

    {

        Console.WriteLine(" number of years = ");

        int n = int.Parse(Console.ReadLine()) ;

        actual = new  double [n];

        forcast =new double [n+1]; 

        for( int i=0; i<n ;i++)

        {

            Console.Write(" the actual demand in year{0} =", i+1);

                actual[i] = int.Parse(Console.ReadLine());

        }

        Console.WriteLine("ALPHA  =  ");

        alpha = int.Parse(Console.ReadLine());

        Console.Write(" forcast first year = ");

        forcast[0]= int.Parse(Console.ReadLine());

    }

     public void ForcastC()

     {

            for(int i=0 ;i<forcast.Length;i++)

            {

                forcast[i] =forcast[i-1]+(alpha*(actual[i-1]-forcast[i-1]));

            }

     }

    public void PErDev()

    {

        perDev = new double[actual.Length];

        for(int i=0 ;i<actual.Length;i++)

        {

            perDev[i]=100*Math.Abs((actual[i]-forcast[i])/actual[i]);

        }

    }

    public void AVDev()

    {

        double sum =0;

        for(int i=0 ;i<PerDev.Length;i++)

        {

            sum =sum +perDev[i];

        }

        avPerDev = sum /actual.Length; 

    }

    public void OutPut()

    {

        Console.Write(" actual     forcast     def");

        for(int i=0 ;i<actual.Length;i++)

        {

            Console.WriteLine(" {0}   {1}   {2} ",actual[i],Math.Round(forcast[i],2),Math.Round(perDev[i],2));

        }

    }

    public void Results()

    {

        Console.WriteLine(" mean =  {0} ",avPerDev);

    }

}