#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
//ifstream fin("date.in");
//ofstream fout("date.out");
//#define cout fout
#define MAX 1002
int a[MAX][MAX];
int josl[MAX][MAX]; //daca va merge in jos si apoi la stanga
int josr[MAX][MAX]; // daca va merge in jos si apoi la dreapta
int l[MAX][MAX]; // daca va merge in stanga
int r[MAX][MAX]; // dava va merge in dreapta

int main()
{
    int n, i, j, mx = -10000;
    cin >> n;
    for(i = 1 ; i <= n ; i++)
    {
        for(j = 1 ; j <= n ; j++)
        {
            cin >> a[i][j];
        }
    }

    for(i = n ; i >= 1 ; i--)
    {
        for(j = 1 ; j <= n ; j++)
        {
            josl[i][j] = max(josl[i + 1][j], max(l[i + 1][j], a[i + 1][j])) + a[i][j];
            josr[i][j] = max(josr[i + 1][j], max(r[i + 1][j], a[i + 1][j])) + a[i][j];
            l[i][j] = max(l[i][j - 1], max(josr[i][j - 1], a[i][j - 1])) + a[i][j];
        }
        for(j = n ; j>= 1 ; j--)
        {
            r[i][j] = max(r[i][j + 1], max(josl[i][j + 1], a[i][j + 1])) + a[i][j];
            mx = max(max(mx, a[i][j]), max(l[i][j], max(r[i][j], max(josl[i][j], josr[i][j]))));
        }


    }
    cout << mx << "\n";
}