#include<bits/stdc++.h>
using namespace std;
int a[1010][1010],f[1010][1010];
int n;
int main(){
	cin >> n;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= i; j++)
			cin >> a[i][j];
	f[1][1] = a[1][1];
	for (int i = 2; i <= n; i++)
		for (int j = 1; j <= i; j++)
			f[i][j] = max(f[i-1][j-1],f[i-1][j]) + a[i][j];
	int ans = 0;
	for (int i = 1; i <= n; i++)
		ans = max(ans, f[n][i]);
	cout << ans;
	return 0;
}