#include <iostream>
using namespace std;
int n,a[1001][1001],qian[1001][1001],ans;
int main()
{
    cin >> n;
    for(int i = 1;i <= n;i ++)
        for(int j = 1;j <= n;j ++)cin >> a[i][j],qian[i][j] = qian[i - 1][j] + qian[i][j - 1] - qian[i - 1][j - 1] + a[i][j];
    for(int i = 1;i <= n;i ++)
        for(int j = 1;j <= n;j ++)
            for(int k = i;k <= n;k ++)
                for(int l = j;l <= n;l ++)
                    ans = max(ans,qian[k][l] - qian[i - 1][l] - qian[k][j - 1] + qian[i - 1][j - 1]);
    cout << ans;
}