//100 p pe Campion si Infoarena (implementare cu cstdio)
#include <iostream>
#include <cstdio>
using namespace std;
const int N=250;
int a[N][N],c[N][N],i,j,n,maxi;
int main()
{
    freopen ("sotron.in","r",stdin);
    freopen ("sotron.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
     for(j=1;j<=n;j++)scanf("%d",&a[i][j]);
    i=1;
    for(j=1;j<=n;j++)
           if((i+j)%2==0) c[i][j]=a[i][j];
                 else c[i][j]=max(a[i][j],a[i][j]+a[i][j+1]);

//  for(i=2;i<=n;i++)
// for(j=n;j>=1;j--)
// if((i+j)%2==0) c[i][j]=max(a[i][j],a[i][j]+c[i-1][j]);
 //                else c[i][j]=max(a[i][j],a[i][j]+c[i][j+1]);
    for(i=2;i<=n;i++)
     for(j=n;j>=1;j--)
       if((i+j)%2==0) if(c[i-1][j]<0)c[i][j]=a[i][j];else c[i][j]=a[i][j]+c[i-1][j];
                 else if(c[i][j+1]<0)c[i][j]=a[i][j];else c[i][j]=a[i][j]+c[i][j+1];
    maxi=-2000000000;
    for(i=1;i<=n;i++)
     for(j=1;j<=n;j++)
           maxi=max(maxi,c[i][j]);
    printf("%d\n",maxi);
    return 0;
}

/*
//80p pe Campion si 100p pe Infoarena
#include <iostream>
#include <fstream>
using namespace std;
ifstream f("sotron.in");
ofstream g("sotron.out");
const int N=250;
int a[N][N],c[N][N],i,j,n,maxi;
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
     for(j=1;j<=n;j++) f>>a[i][j];
    i=1;
    for(j=1;j<=n;j++)
           if((i+j)%2==0) c[i][j]=a[i][j];
                 else c[i][j]=max(a[i][j],a[i][j]+a[i][j+1]);


    for(i=2;i<=n;i++)
     for(j=n;j>=1;j--)
       if((i+j)%2==0) c[i][j]=max(a[i][j],a[i][j]+c[i-1][j]);
                 else c[i][j]=max(a[i][j],a[i][j]+c[i][j+1]);
  //  for(i=2;i<=n;i++)
  //   for(j=n;j>=1;j--)
  //     if((i+j)%2==0) if(c[i-1][j]<0)c[i][j]=a[i][j];else c[i][j]=a[i][j]+c[i-1][j];
  //               else if(c[i][j+1]<0)c[i][j]=a[i][j];else c[i][j]=a[i][j]+c[i][j+1];
    maxi=-2000000000;
    for(i=1;i<=n;i++)
     for(j=1;j<=n;j++)
           maxi=max(maxi,c[i][j]);
    g<<maxi<<'\n';
    f.close();g.close();
    return 0;
}
*/