using System;

public class Program

{

    public static void Main()

    {

        var number = -1234567890;

        Console.WriteLine("Method SumDigits1 = "+ SumDigits1(Math.Abs(number)).ToString());

        Console.WriteLine("Method SumDigits2 = "+ SumDigits2(Math.Abs(number)).ToString()); 

        Console.WriteLine("Method SumDigits3 = "+ SumDigits3(Math.Abs(number)).ToString()); 

    }

    public static int SumDigits1(int n)

    {

        int sum = 0;

        int rem;

        while (n != 0)

        {           

            n = Math.DivRem(n, 10, out rem);

            sum += rem;

        }

        return sum;

    }

    public static int SumDigits2(int n)

    {

        int sum = 0;

        int rem;

        for (sum = 0; n != 0; sum += rem)   

            n = Math.DivRem(n, 10, out rem);        

        return sum;

    }   

    public static int SumDigits3(int n)

    {

        int sum = 0;    

        while (n != 0)

        {

            sum += n % 10;

            n /= 10;

        }   

        return sum;

    }   

}