//poj1050

//n^4暴力

#include<algorithm>

#include<cstdio>

#include<cstring>

#include<cmath>

#define N 105

#define INF 0x3fffffff

using namespace std;

int a[N][N];

int sum[N];

int ans;

int main()

{

    int n; scanf("%d", &n);

    for (int i = ; i <= n; i++)

        for (int j = ; j <= n; j++)

            scanf("%d", &a[i][j]);

    for (int i = ; i <= n; i++) {

        memset(sym, , sizeof(sum));

        for (int j = i; j <= n; j++) {

            int num = ;

            for (int k = ; k <= n; k++) {

                num += sum[k] += a[j][k];

                ans = max(ans, num);

                if (num < ) num = ;

            }

        }

    }

    printf("%d\n", ans);

    return ;

}