#include<iostream>
//#include<vector>
#include<algorithm>

using namespace std;
int tri[500][500];
const int down_left=0,down_right=1,up_left=-1,up_right=0;
int i=1;

void solve_pro( )
{
    int k;
    int sum=0;
    for(int j=0;j!=i-1;j++)
    {
        sum;
        int b;
        int a = tri[i-2][j];
        b = max(tri[i-1][j+down_left],tri[i-1][j+down_right]);
  //      cout<<a<<" "<<b<<endl;
        if( sum < a+b )
        {
            sum = a+b;
          //  h = i-1;
            k = j;
 //          cout<<sum<<endl;
        }
    }
    i=i-2;
    while( i-- )
    {
        if( k >= 0 )
        {
            sum += max(tri[i][k+up_left],tri[i][k+up_right]);
            if(tri[i][k+up_left] >= tri[i][k+up_right])
                k = k + up_left;
            else
                k = k + up_right;
        }

        else
            sum +=tri[i][k+up_right];
    }

    cout<<sum<<endl;
}
int main()
{
    int num;
    cin>>num;
    while( num-- )
    {
        for(int j=0;j!=i;j++)
        {
            cin>>tri[i][j];
        }
        i++;
    }
    solve_pro();
    return 0;
}