#include<iostream>
#include<cmath>
#include<algorithm>
#include<queue>
using namespace std;
using ll = long long;
const int N = 1e3+10;
ll a[N][N],sum;
int main()
{
    ll sum = 0;
   int r;cin>>r;
   for(int i = 1;i <= r;i++)
   {
        for(int j = 1;j <= i;j++)
        {
            cin>>a[i][j];
        }
   }

   for(int i = 2;i <= r;i++)
   {
        for(int j = 1;j <= i;j++)
        {
            //一定要注意考虑边界值
            if(j == 1)
            {
                a[i][j] += a[i-1][j];
            }
            else if(j == i)
            {
                a[i][j] += a[i-1][j-1];
            }
            else 
            {
                a[i][j] += max(a[i-1][j],a[i-1][j-1]);
            }
        }
        
   }
   for(int j = 1; j <= r;j++)
   {
        sum = max(sum,a[r][j]);
   }
   cout<<sum<<"\n";
    return 0; 
}