#include <cstdio>
#include <algorithm>
#include<cstring>
#include<iostream>
using namespace std;
const int MAX = 400;
int a[MAX][MAX];
int d[MAX][MAX];
int n;
int solve(int i ,int j)
{
if(d[i][j]>=0)
return d[i][j];
return d[i][j] = a[i][j] +(i==n?0:max(solve(i+1,j),solve(i+1,j+1)));
}
int main()
{
scanf("%d",&n);
for(int i=0;i<n;i++)
{
for(int j=0;j<=i;j++)
{
scanf("%d",&a[i][j]);
}
}
memset(d,-1,sizeof(d));
int len = solve(0,0);
printf("%d",len);
}
