using System;
using System.Linq;

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

            while (nums.Length > 0)
            {
                int[] condensed = new int [nums.Length - 1];
                for (int i = 0; i < nums.Length - 1; i++)
                {
                    condensed[i] = nums[i] + nums[i + 1];
                }
                Console.WriteLine(condensed.Sum());
                break;
            }

        }
    }
}