using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

            //Declaration of Expense Report List

            List<int> expense_report_list = new List<int>() { 1721, 979, 366, 299, 675, 1456 };

            //Declaration of sum integer

            int sum = 0;

            //Iterate through sequece in collection

            foreach (int seq1 in expense_report_list)

            {

                foreach (int seq2 in expense_report_list)

                {

                    if(seq1 + seq2 == 2020)

                    {

                        sum = seq1 * seq2;

                    }

                }

            }

​

            //Print results

            Console.Write(sum);

    }

}