#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 10;
int f[N];
int a[N][N];
int main() {
    int n;
    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++)
            f[j] = max(f[j + 1], f[j]) + a[i][j];

    printf("%d", f[1]);
    return 0;
}