//I received an error: Crash (ACCESS_VIOLATION) from the judge

// USU Problem 1146
// Maximum Sum
// Done by Teh Ming Han

#include <iostream.h>
#include <fstream.h>

int main(){
   int x1,y1,x2,y2,n,c,max=0;
   int sum[100][100], work[100][100]={0};

   ifstream infile("maxsum.in");
   infile>>n;
   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         infile>>sum[x1][y1]; //read data
   infile.close();

   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         for (x2=1;x2<=x1;x2++)
            for (y2=1;y2<=y1;y2++)
               work[x1][y1] += sum[x2][y2];

   for (x1=1;x1<=n;x1++)
      for (y1=1;y1<=n;y1++)
         for (x2=x1;x2<=n;x2++)
            for (y2=y1;y2<=n;y2++){
               c = work[x2][y2] - work[x1-1][y2] - work[x2][y1-1] +
work[x1-1][y1-1];
               if (c>max) max=c;
            }

   ofstream outfile("maxsum.out");
   outfile<<max;
   outfile.close();
   return 0;
}