#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef pair<int, int> PII;
using ll = long long;
using ULL = unsigned long long;
const int N = 1e7 + 5;

int n,a[1010][1010];
inline void solve() {
    cin >> n;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= i; j++) 
            cin >> a[i][j];
    for (int i = n - 1; i >= 1; i--) {
        for (int j = 1; j <= i; j++) {
             a[i][j] = max(a[i][j]+a[i+1][j],a[i][j]+a[i+1][j+1]);
        }
    }        
    cout << a[1][1] << endl;
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int _ = 1;
    //int _; cin >> _;
    while (_--) solve();
    return 0;
}