import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;

public class Main {
    static int INF = Integer.MIN_VALUE;

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[][] mp = new int[n+10][n+10];
        int[][] dp = new int[n+10][n+10];
        for(int i = 1; i <= n ; i++){
            for(int j = 1 ; j <= i ; j++){
                mp[i][j] = sc.nextInt();
            }
        }
        for(int i = n ; i >= 1 ; i--){
            for(int j = 1 ; j <= i ; j++){
                if( i == 1 ){
                    dp[i][j] = mp[i][j];
                }
                dp[i][j] = Math.max(dp[i+1][j] , dp[i+1][j+1])+ mp[i][j];
            }
        }
        System.out.println(dp[1][1]);






    }
}