#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 10;
int a[N][N], dp[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];
		}
	}
	int mans = 0;
	dp[1][1] = a[1][1];
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= i; j++) {
			dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - 1] + a[i][j]);
			if (dp[i][j] > mans)
				mans = dp[i][j];
		}
	}
	cout << mans;
	return 0;
}