using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _08.Condense_Array_to_Number
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();

            while(arr.Length>1)
            {
                int[] condensed = new int[arr.Length - 1];
                for (int i = 0; i < arr.Length; i++)
                {
                    if (i == arr.Length-1)
                    {
                        break;
                    }
                    condensed[i] = arr[i] + arr[i + 1];

                }
                arr = condensed;
            }
            Console.WriteLine(string.Join("", arr).ToArray());
        }
    }
}