using System;

public class Program

{

    public static void Main()

    {

        int[] array = {0,1,2,3,4,5,3};

        int x = Program.Calc(array,0,0);

        Console.WriteLine(x);

​

    }

    public static int Calc (int[] arr, int n1, int n2) {

        int sum = 0;

        for(int i= n1; i <= n2 ; i++){

            sum += arr[i];

        }

        return sum;

    }

}