using System;

​

public class Program

{

    public static int sumdigits(int n)

        {

            if (n == 0) return 0;

            return sumdigits(n/10)+n%10;

        }

​

    public static int sum(int n)

        {

            int result;

            if (n == 1) result = 1;

            else result = n + sum(n-1);

            return result;

        }

    public static float power(float x, float n)

        {

        if(n>0)

            {

                return x*power(x,n-1);

            }

        else if(n==0)

            {

                return 1;

            }

        else if(n<0)

            {

                return 1/power(x, Math.Abs(n));

            }

                return -1;

            }

​

​

    public static void Main()

        {

            Console.WriteLine(sumdigits(123));

            Console.WriteLine(sum(5));

            Console.WriteLine(power(2,2));

​

        }

}