using System;

public class Program

{

    public static void Main()

    {

        int[] arr = new int[]{12,5,7,3};

        Console.WriteLine(sumarray(arr));

    }

    public static int sumarray(int[] arr)

    {

        return sumarray(arr,0,0);

    }

    public static int sumarray(int[] arr, int i , int sum)

    {

        if (i == arr.Length) return 0;

        return arr[i] += sumarray(arr, i + 1,sum);

    }   

}