/*
最大子矩阵
*/
#include < iostream >
using   namespace  std;

int  N;
int  s[ 101 ][ 101 ];
int  Max;
int  main()
{
    cin >> N;
     for ( int  i = 1 ;i <= N; ++ i)
        s[i][ 0 ] = 0 ;
     for ( int  i = 1 ;i <= N; ++ i)
         for ( int  j = 1 ;j <= N; ++ j){
            cin >> s[i][j];
            s[i][j] += s[i][j - 1 ];
        }
    Max =- 0xFFFFFFF ;
     int  m;
     for ( int  k = 1 ;k <= N; ++ k)
         for ( int  i = k;i <= N; ++ i){
            m = s[ 1 ][i] - s[ 1 ][k - 1 ];
             if (m > Max) Max = m;
             for ( int  j = 2 ;j <= N; ++ j){
                 if (m < 0 ) m = s[j][i] - s[j][k - 1 ];
                 else  m += s[j][i] - s[j][k - 1 ];
                 if (m > Max) Max = m;
            }
        }
    cout << Max << endl;
     return   0 ;
}