using System;

public class Program

{

        public static long[,] a;

    public static long n;

    public static long getSum(long i, long j){

        long r1,r2;

        if (i<(n-1)){

            r1 =a[i,j]+ getSum(i+1,j);

            r2 =a[i,j]+ getSum(i+1,j+1);        

        }

        else{

            r1=a[i,j];

            r2=a[i,j];

        }

        return r1>r2?r1:r2;

    }

    public static void Main()

    {

        long[,] a1= {   

            {1,-1,-1,-1},

            {8,4,-1,-1},

            {2,6,9,-1},

            {8,5,9,3}

        };  

        a=a1;

        n =a.GetLength(0);

        Console.WriteLine(getSum(0,0));

    }

}