/*
ID: mycodeb1
LANG: C++
TASK: numtri
*/
 
#include <cstdio>
#include <stack>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <functional>
#include <cstring>
#include <algorithm>
#include <cctype>
#include <ctime>
#include <cstdlib>
#include <fstream>
#include <string>
#include <sstream>
#include <map>
#include <cmath>
#define LL long long
#define lowbit(x) ((x) & (-x))
#define MP(a, b) make_pair(a, b)
#define MS(arr, num) memset(arr, num, sizeof(arr))
#define PB push_back
#define F first
#define S second
#define ROP freopen("input.txt", "r", stdin);
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
using namespace std;
const int MAXN = 1000 + 5;
 
typedef pair<int, int> pii;
typedef vector<int>::iterator viti;
typedef vector<pii>::iterator vitii;
 
int mp[MAXN][MAXN];
 
int main()
{
    //ROP;
    freopen("numtri.in", "r", stdin);
    freopen("numtri.out", "w", stdout);
 
    int n, i, j;
    scanf("%d", &n);
    for (i = 1; i <= n; i++)
        for (j = 1; j <= i; j++) scanf("%d", ∓[i][j]);
    for (i = n - 1; i >= 1; i--)
        for (j = 1; j <= i; j++)
            mp[i][j] = max(mp[i + 1][j], mp[i + 1][j + 1]) + mp[i][j];
    printf("%d\n", mp[1][1]);
    return 0;
}