01.Sum to 13

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Softuniada_2017
{
    class Program
    {
        static string output = "No";
        static void Main(string[] args)
        {
            int[] numbers = Console.ReadLine()
                           .Split()
                           .Select(int.Parse)
                           .ToArray();

            IsSumAchievable(numbers , 0);
            Console.WriteLine(output);

        }

        static void IsSumAchievable(int[] numbers,int index)
        {
            if (index == 3)
            {
                return;
            }
            for (int i = 0; i < 2 && output == "No"; i++)
            {
                numbers[index] = i == 0 ? Math.Abs(numbers[index]) : 0 - Math.Abs(numbers[index]);
                int sum = numbers.Sum();
                if (sum == 13)
                {
                    output = "Yes";
                    return;
                }
                else
                {
                    IsSumAchievable(numbers, index + 1);
                }
            }
        }
    }
}