import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.Collections;

import java.util.StringTokenizer;

/*

ID: mryuan01

LANG: JAVA

TASK: numtri

*/

public class numtri {

public static int[][] numT = null;

public static int[][] result = null;

public static void dp(){

for(int i = 0; i < numT.length; i++){

for(int j = 0; j < numT[i].length; j++){

int max = Integer.MIN_VALUE;

if(i - 1 < 0){

max = 0;

}else if(j - 1 < 0){

max = result[i - 1][j];

}else if(j > i - 1){

max = result[i - 1][j - 1];

}else{

if(result[i - 1][j] > result[i - 1][j - 1])

max = result[i - 1][j];

else

max = result[i - 1][j - 1];

}

result[i][j] = numT[i][j] + max;

}

}

}

static int collectOutput(){

int max = Integer.MIN_VALUE;

for(int i = 0; i < result[result.length - 1].length; i++){

if(max < result[result.length - 1][i])

max = result[result.length - 1][i];

}

return max;

}

public static void main(String[] args) throws IOException {

BufferedReader f = new BufferedReader(new FileReader("numtri.in"));

// input file name goes above

PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("numtri.out")));

int len = Integer.parseInt(f.readLine().trim());

numT = new int[len][];

result = new int[len][];

for(int i = 0; i < len; i++){

numT[i] = new int[i+1];

result[i] = new int[i+1];

StringTokenizer st = new StringTokenizer(f.readLine().trim());

for(int j = 0; j <= i; j++){

numT[i][j] = Integer.parseInt(st.nextToken());

}

}

dp();

int ret = collectOutput();

out.println(ret);

out.close();

}

}