using System;

public class Program

{

    public static void Main()

    {

        try

        {

            Console.WriteLine("Informe o valor de i: ");

            double i = double.Parse(Console.ReadLine());

            Console.WriteLine("Informe o valor de n: ");

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

            double y = i;

            for(int x = 2; x <= n; x++)

            {

                y = y - (Math.Pow(i,x) + Math.Pow(i,(x+1)));

                x++;

            }

            Console.WriteLine("O valor de y = " + y);

        }

        catch(Exception ex)

        {

            Console.WriteLine(ex.Message);

        }

    }

}