#include<iostream>
int a[1005][1005],dp[1005][1005];
using namespace std;
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 = 1; i <= n; i++)
	{
		dp[n][i] = a[n][i];
	}
	for (int i = n - 1; i  >=1; i--)
	{
		for (int j = 1; j <= n-i+1; j++)
		{
			dp[i][j] = max(dp[i + 1][j], dp[i + 1][j + 1])+a[i][j];
		}
	}
	cout << dp[1][1];
	return 0;
}