#include <algorithm>
#include <iostream>
using namespace std;
const int N = 510;
int f[N][N];
int g[N][N];

int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= i; j++)
      cin >> g[i][j];

  for (int i = 1; i <= n; i++)
    f[n][i] = g[n][i];

  for (int i = n - 1; i >= 1; i--)
    for (int j = 1; j <= i; j++)
      f[i][j] = max(f[i + 1][j], f[i + 1][j + 1]) + g[i][j];

  cout << f[1][1] << endl;

  return 0;
}