#include <bits/stdc++.h>
using namespace std;
int c[1001][1001], s[1001][1001];

int main() {
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			cin >> c[i][j];
			s[i][j] += s[i - 1][j] + s[i][j - 1] + c[i][j] - s[i - 1][j - 1];
		}
	}
	int ans = -2147483647;
	for (int x = 1; x <= n; ++x) {
		for (int y = 1; y <= n; ++y) {
			for (int x2 = x + 1; x2 <= n; ++x2) {
				for (int y2 = y + 1; y2 <= n; ++y2) {
					ans = max(s[x2][y2] - s[x - 1][y2] - s[x2][y - 1] + s[x - 1][y - 1], ans);
				}
			}
		}
	}
	cout << ans;
	return 0;
}