#include <stdio.h>
int main()
{int n,i,j,c[101][101],max,s,q;

 freopen("joctv.in","r",stdin);
 freopen("joctv.out","w",stdout);
 scanf("%d",&n);max=-100000;
 for (i=1;i<=n;i++)
	 for (j=1;j<=n;j++)
		{scanf("%d",&s);
	     c[i][j]=c[i-1][j]+s;
		}		 
 
for (i=1;i<=n;i++)
 for (j=i;j<=n;j++)
 {s=0;
	 for (q=1;q<=n;q++)
      if ((s+c[j][q]-c[i-1][q])>(c[j][q]-c[i-1][q]))
       {s+=c[j][q]-c[i-1][q];
	    if (s>max) max=s;}  else
			{s=c[j][q]-c[i-1][q];
	    if (s>max) max=s;}
 }
 printf("%d",max);
 return 0;}