using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

            string code = "4 6 9 1 5 4 6 9 2 1 2 9 8";

            long[] digets = code.Split(' ').Select(long.Parse).ToArray();

            // 1

            long resultOne = 0;

            int i = 0;

            foreach (var num in digets)

            {

                if (((i + 1) % 2) == 0) {

                    resultOne += num;

                }

                i++;

            }

            // 2

            resultOne = resultOne * 3;

            // 3

            long resultTwo = 0;

            int s = 0;

            foreach (var num in digets)

            {

                if ((s % 2) == 0) {

                    resultTwo += num;

                }

                s++;

            }

            resultTwo = resultTwo - digets.Last();

            // 4

            long result = resultOne + resultTwo;

            // 5

            result = result % 10;

            // 6

            result = 10 - result;

            // Результат

            Console.WriteLine(result);

    }

}