#include<cstdio>

int a[1024][1024],b[1024],c[1024],n,i,j;
int ma(int x, int y)
{
    if(x > y)
        return x;
    return y;
}
int main()
{
    freopen("B.in","r",stdin);
    freopen("B.out","w",stdout);

    scanf("%d",&n);

    for(i=1;i<=n; ++i)
    {
        for(j=1;j<=n;++j)
        {
            scanf("%d\n",&a[i][j]);
        }
    }

    for(i = 0; i <= n+1; ++i)
    {
        a[0][i] = -1024;
        a[n+1][i] = -1024;
        a[i][0] = -1024;
        a[i][n+1] = -1024;
    }

    for(i=1;i<=n; ++i)
    {
        for(j = 1; j <= n; ++j)
        {
            b[j] = a[i][j];
            b[j] = ma(b[j], a[i-1][j] + a[i][j]);
            b[j] = ma(b[j], b[j-1] + a[i][j]);
        }

        for(j = n; j>=1; --j)
        {
            c[j] = a[i][j];
            c[j] = ma(c[j], a[i-1][j] + a[i][j]);
            c[j] = ma(c[j], c[j+1] + a[i][j]);
        }

        for(j = 1; j <= n; ++j)
        {
            a[i][j] = ma(b[j],c[j]);
        }
    }
    int rez = -1024;
    for(i=1; i<=n; ++i)
    {
        for(j = 1; j<=n; ++j)
        {
            if(a[i][j] > rez)
            {
                rez = a[i][j];
            }
        }
    }
    printf("%d\n",rez);



    return 0;
}