CondenseArrayToNumber

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

namespace CondenseArrayToNum
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr = Console.ReadLine()
               .Split()
               .Select(int.Parse)
               .ToArray();
            int[] condArr = new int[arr.Length - 1];

            if (arr.Length == 1)
            {
                Console.WriteLine(arr[0]);
            }
            else if (arr.Length > 1)
            {
            for (int i = 0; i < arr.Length; i++)
            {
                for (int j = 0; j < condArr.Length - i; j++)
                {
                    condArr[j] = arr[j] + arr[j + 1];
                }
                arr = condArr;
            }
            Console.WriteLine(condArr[0]);
            }
        }
    }
}