using System;

using System.Collections.Generic;

using System.IO;

​

namespace ConsoleApp1

{

    class Program

    {

        static void Main(string[] args)

        {

            var numbers = new List<int>();

            using (StreamReader sr = File.OpenText(@"C:/temp/someInput.txt"))

            {

                string s = String.Empty;

                while ((s = sr.ReadLine()) != null)

                {

                    numbers.Add(int.Parse(s));

                }

            }

​

            Console.WriteLine("Here is a result: ");

            foreach (var number1 in numbers)

            {

                foreach (var number2 in numbers)

                {

                    foreach (var number3 in numbers)

                    {

                        if (number1 + number2 + number3 == 2020)

                        {

                            Console.WriteLine($"{number1} + {number2} + {number3} = {number1 + number2 + number3}");

                            Console.WriteLine($"{number1} * {number2} * {number3} = {number1 * number2 * number3}");

                        }

                    }

                }

            }

        }

    }

}