#include<stdio.h>

long  mx,Matrix[1010][1010],i,j,k,y,sum,dim;

int main()
{

    while(scanf("%ld",&dim)==1)
    {
        mx=-99999;sum=0;
        for(i=0;i<101;i++)
          for(j=0;j<101;j++)
             Matrix[i][j]=0;

        for(i=1;i<=dim;i++)

            for( j = 1 ; j <= dim ; j++)

            {
                scanf("%ld", &Matrix[i][j]);

                Matrix[i][j]+= Matrix[i][j-1] + Matrix[i-1][j] - Matrix[i-1][j-1];

                if(mx < Matrix[i][j])
                    mx = Matrix[i][j];
            }

        for(i = 1; i <= dim ; i++)

            for(j = 1; j <= dim ; j++)

                for( y = 1; y < i ; y++)

                    for( k = 1 ; k < j ; k++)

                    {
                        sum = Matrix[i][j] - Matrix[i][k-1] - Matrix[y-1][j] + Matrix[y-1][k-1];

                        if(mx < sum)
                            mx = sum;
                        sum = 0;
                    }
        printf("%ld\n",mx);
    }
    return 0;
}