#include<cstdio>
#include<algorithm>
using namespace std;
const int nmax = 55;
int n,i,j,k,a[nmax][nmax],l[nmax][nmax],c[nmax][nmax],sol,dif;
int main()
{
	//freopen("test.in","r",stdin);
	//freopen("test.out","w",stdout);
    scanf("%d",&n); sol=1<<31;
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++) scanf("%d",&a[i][j]),sol=max(sol,a[i][j]);
    for(i=1;i<=n;i++)
        for(j=1;j<=n;j++)
        {
            l[i][j]=l[i][j-1]+a[i][j];
            c[i][j]=c[i-1][j]+a[i][j];
        }
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
        {
            dif=j-i+1;
            for(k=dif;k<=n;k++)
                sol=max(sol,l[i][k]+l[j][k]-l[i][k-dif]-l[j][k-dif]+c[j-1][k]+c[j-1][k-dif+1]-c[i][k]-c[i][k-dif+1]);
        }
    printf("%d\n",sol);
	return 0;
}