#include <bits/stdc++.h>
using namespace std;
const int N = 130;
int a[N][N], s[N][N];
int main() {
    int n, res = INT_MIN;
    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] + a[i][j];
        }

    for (int i = 1; i <= n; ++i) {
        for (int j = 0; j < i; ++j) {
            int _s = 0;
            for (int k = 1; k <= n; ++k) {
                _s = max(_s, 0) + s[i][k] - s[j][k];
                res = max(res, _s);
            }
        }
    }
    cout << res << '\n';
    return 0;
}