using System;

using System.Collections.Generic;

using System.Text;

public class Program

{

    public static void Main(string[] args)

    {

        var integers = new List<int> { 10, 5, 2, 7, 7, 49 };

​

        for (int indexOf1stNumber = 0; indexOf1stNumber < integers.Count; indexOf1stNumber++)

        {

            for (int indexOf2ndNumber = indexOf1stNumber + 1; indexOf2ndNumber < integers.Count; indexOf2ndNumber++)

            {

                var sum = integers[indexOf1stNumber] + integers[indexOf2ndNumber];

                foreach (var number in integers)

                {

                    if (sum == number)

                    {

                        var pair = new StringBuilder();

                        pair.Append("(").Append(integers[indexOf1stNumber]).Append(", ").Append(integers[indexOf2ndNumber]).Append(")");

                        Console.WriteLine(pair.ToString());

                        break;

                    }

                }

            }

        }

    }

}

​