#include<utility>
#include<algorithm>
#include<queue>
#include<stack>
#include<cstdio>
#include<cmath>
#include<iostream>
#include<string.h>
#include<stdio.h>
#include<iomanip>
#include<cstring>
#include<math.h>
#include<vector>
#include<stdio.h>
using namespace std;
#define ll long long
const int N = 1e3 + 10;
const int INF = 0x3f3f3f3f;
int n , a[N][N] , dp[N][N];
int main()
{
	cin >> n;
	for ( int i = 1 ; i <= n ; i++ )
	{
		for(int j=1;j<=i;j++)
		{
			cin>>a[i][j];
		}
	}
	for ( int i = n ; i >= 1 ; i-- )
	{
		for ( int j = 1 ; j <= i ; j++ )
		{
			dp[i][j] = max( dp[ i + 1 ][j] , dp[ i + 1 ][ j + 1 ] ) + a[i][j];
		}
	}
	cout << dp[1][1];
	return 0;
}