#include <stdio.h>

int c[101][101];
int n,nr;
long s,max,sum;

void read_solve ()
{
    int i,j,k,l,p,q,min;
    
    scanf ("%d",&n);
    
    for (i=1; i<=n; ++i)
        for (j=1; j<=n; ++j)
        {
            scanf ("%d",&nr);
            s+=nr;
            c[i][j]=s;
        }
    
    for (i=1; i<=n; ++i)
        for (j=1; j<=n; ++j)
        {
            min=c[i-1][j-1];
            for (k=11; k<i; ++k)
                for (l=1; l<j; ++l)
                    if (c[k][l]<=min)
                        min=c[k][l];
            sum=c[i][j]-min;
            if (sum>max)
                max=sum;
        }    
            
    printf ("%d",max);
}

int main ()
{
	freopen ("secv.in","r",stdin);
	freopen ("secv.out","w",stdout);
	read_solve ();
	return 0;
}