#include<iostream>
using namespace std;
const int N = 110;
int a[N][N], s[N][N];
int main()
{
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            cin >> a[i][j];
            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j];
        }
    }

    int mx = -0x3f3f3f3f;
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            for(int ii = i; ii <= n; ii++)
            {
                for(int jj = j; jj <= n; jj++)
                {
                    mx = max(mx, s[ii][jj] - s[i - 1][jj] - s[ii][j - 1] + s[i - 1][j - 1]);
                }
            }
        }
    }

    cout << mx << endl;

    return 0;
}