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

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