#include <iostream>

using namespace std;

const int N = 505;

int q[N][N];

int main() {
    int n;
    cin >> n;

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j <= i; ++j) {
            cin >> q[i][j];
        }
    }

    for (int i = n - 2; ~i; --i) {
        for (int j = 0; j <= i; ++j) {
            q[i][j] += max(q[i+1][j], q[i+1][j+1]);
        }
    }
    cout << q[0][0] << endl;

    return 0;
}