#include <cstdio>

#include <string>

#include <cstdlib>

#include <cmath>

#include <iostream>

#include <cstring>

#include <set>

#include <queue>

#include <string>

#include <algorithm>

#include <vector>

#include <map>

using namespace std ;

typedef long long LL;

typedef pair<int, int> P;

const int INF = 0x3f3f3f3f;

const double inf = 0x3f3f3f3f3f3f3f;

const int maxn = 350 + 5;

int a[maxn][maxn];

int d[maxn][maxn];

int main(){

    int n;

    scanf("%d", &n);

    for(int i = 0; i < n; ++i)

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

            scanf("%d", &a[i][j]);

    for(int i = n-1; i >= 0; --i){

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

            d[i][j] = max(d[i+1][j], d[i+1][j+1]) + a[i][j];

    }

    printf("%d\n", d[0][0]);

    return 0;

}