Condense Array to Number

using System;
using System.Linq;

namespace GitHub
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] arr1 = new int[] { 5,1,4,1,2 };
            int[] arr2 = new int[arr1.Length - 1];
            if (arr1.Length == 1)
            {
                Console.WriteLine(arr1[0]);
                return;
            }
            for (int first = 0; first < arr1.Length; first++)
            {
                Console.Write(arr1[first] + " ");
                for (int second = 0; second < arr2.Length - first; second++)
                {
                    arr2[second] = arr1[second] + arr1[second + 1];

                }
                arr1 = arr2;
            }
            Console.WriteLine("\nSum= " + arr1[0]);

        }
    }
}