using System;

public class Program

{

    public static void Main()

    {

            Console.Write("Введiть а: ");

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

            int b = 0;

            if (a % 2 == 0)

            {

                for (int i = b; i <= a; i = i + 2)

                {

                    Console.WriteLine(i + " ");

                    b = i + b;

                }

                Console.WriteLine("сума = " + b);

            }

            else

            {

                a = a - 1;

                for (int i = b; i <= a; i = i + 2)

                {

                    Console.WriteLine(i + " ");

                    b = i + b;

                }

                Console.WriteLine("сума = " + b);

            }

    }

}