/*
    Look at me!
    Look at me!
    Look at how large the monster inside me has become!
*/
#include<fstream>
#include<iostream>
#include<cstdio>
#include<map>
#include<typeinfo>
#include<set>
#define FIT(a,b) for(vector<int >::iterator a=b.begin();a!=b.end();a++)
#define FITP(a,b) for(vector<pair<int,int> >::iterator a=b.begin();a!=b.end();a++)
#define RIT(a,b) for(vector<int>::reverse_iterator a=b.end();a!=b.begin();++a)
#include<stack>
#define ROF(a,b,c) for(int a=b;a>=c;--a)
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#define REP(a,b) for(register int a=0;a<b;++a)
#include<cstring>
#include<bitset>
#include<cmath>
#include<iomanip>
#define f cin
#define g cout
#include<queue>
#define INF 0x3f3f3f3f
#define debug cerr<<"OK";
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ld long double
#define ll long long
#define ull unsigned long long
#define eps 1.e-7
#define BUFMAX 10100100
#define M 100100
#define N 1010
#define NM 2000100
#define mod 1000000007
#define eps 1.e-10
using namespace std;
/*
int dx[]={-1,-1,-1,0,1,1,1,0};
int dy[]={-1,0,1,1,1,0,-1,-1};
*/

int n,D[2][N],L[2][N],l[2][N],r[2][N],R[2][N],p,sol;

int main ()
{

    #ifndef ONLINE_JUDGE
    freopen("a.in","r",stdin);
    freopen("a.out","w",stdout);
    #endif

    f>>n;
    p=1;
    sol=-(1<<30);
    FOR(i,1,n)
    {
        if(i==3)
        {
            i++;
            i--;
        }
        FOR(j,1,n)
        f>>D[p][j];
        FOR(j,1,n)
        {
            L[p][j]=R[1-p][j]+D[p][j];
            l[p][j]=max(L[1-p][j],R[1-p][j])+D[p][j];
            if(j!=1)
                L[p][j]=max(L[p][j],D[p][j]+L[p][j-1]);
            L[p][j]=max(L[p][j],D[p][j]);
        }
        ROF(j,n,1)
        {
            R[p][j]=L[1-p][j]+D[p][j];
            r[p][j]=max(R[1-p][j],L[1-p][j])+D[p][j];
            if(j!=n)
                R[p][j]=max(R[p][j],D[p][j]+R[p][j+1]);
            R[p][j]=max(R[p][j],D[p][j]);
        }
        FOR(j,1,n)
        {
            sol=max(sol,max(R[p][j],L[p][j]));
            R[p][j]=max(R[p][j],r[p][j]);
            L[p][j]=max(L[p][j],l[p][j]);
        }
        p=1-p;
    }
    g<<sol;
    return 0;
}