using System;

using System.Collections.Generic;

​

public class TwoSum

{

    public static Tuple<int, int> FindTwoSum(IList<int> list, int sum)

    {

        for(int i = 0; i < list.Count; i++){

            for(int j = 1; j < list.Count - 1; j++) {

                if(list[i] + list[j] == sum) return new Tuple<int, int>(i, j);

            }

        }

        return null;

    }

​

    public static void Main(string[] args)

    {

        Tuple<int, int> indices = FindTwoSum(new List<int>() { 1, 3, 5, 7, 9 }, 12);

        Console.WriteLine(indices.Item1 + " " + indices.Item2);

    }

}