#include<iostream>
using namespace std;
int temp[1001][1001];
int main()
{
	int n;
	scanf("%d",&n);
	for(int i = 0; i < n ; i++)
	{
	    for(int j=0;j<=i;j++)
		{
			scanf("%d",&temp[i][j]); 
		}	
	}
	int ans = temp[0][0];
	for(int i = 1;i < n;i++){
		for(int j = 0;j <= i; i++){
			if(j == 0) temp[i][j] = temp[i-1][j] + temp[i][j];
			else 
			{
				temp[i][j] = max(temp[i-1][j-1] , temp[i][j-1]) + temp[i][j];
				ans = max(ans,temp[i][j]);
			}
		}
	}
	cout<<ans;
	return 0;
}