#include<iostream>
#include<cstdio> 
using namespace std;
int a[1001][1001],f[1001][1001];
inline int maxx(int a,int b)
{
	if(a>b)return a;
	else return b;
}
int main()
{
	int n;
	scanf("%d",&n);
	for(register int i=1;i<=n;i++)
		for(register int j=1;j<=i;j++)
		{
			scanf("%d",&a[i][j]);
			f[i][j]=a[i][j];
		}
	for(register int i=n;i>=1;i--)
		for(register int j=1;j<=n;j++)
		{
			f[i][j]=maxx(f[i+1][j],f[i+1][j+1])+a[i][j];
		}
	printf("%d",f[1][1]);
	return 0;
}