#include <fstream>
using namespace std;
ifstream f("joctv.in");
ofstream g("joctv.out");
int C[101][101];
int main()
{
    int n, i, j, l, c, k, max, best, aux;
    max = -2000000000;
    f >> n;
    for(i = 1; i <= n; i++)
        for(j = 1; j <= n; j++){
            f >> C[i][j];
            C[i][j] += C[i-1][j];
        }
    for(i = 1; i <= n; i++)
        for(j = i; j <= n; j++){
            best = 0;
            for(k = 1; k <= n; k++){
                aux = C[j][k]-C[i-1][k];
                if( best + aux > aux )
                    best = best + aux;
                else
                    best = aux;
            }
            if(max < best)
                max = best;
        }

    g << max;
    return 0;
}