// Author: btjanaka (Bryon Tjanaka)

// Problem: (UVa) 108

#include <bits/stdc++.h>

using namespace std;

int arr[110][110];

int main() {

// Input

int n;

while (scanf("%d", &n) > 0) {

for (int i = 0; i < n; ++i) {

for (int j = 0; j < n; ++j) {

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

if (i > 0)

arr[i][j] += arr[i - 1][j]; // Add the rectangle from the top

if (j > 0)

arr[i][j] += arr[i][j - 1]; // Add the rectangle from the left

if (i > 0 && j > 0) arr[i][j] -= arr[i - 1][j - 1];

}

}

// Print out board

// for (int i = 0; i < n; ++i) {

// for (int j = 0; j < n; ++j)

// printf("%2d ", arr[i][j]);

// putchar('\n');

//}

// Calculate the sums

int mx = -1000000000;

for (int x0 = 0; x0 < n; ++x0) {

for (int y0 = 0; y0 < n; ++y0) {

for (int x = x0; x < n; ++x) {

for (int y = y0; y < n; ++y) {

// Calculate sum; compare to mx

// x0 and y0 mark left top corner of matrix.

// x and y mark bottom right corner of matrix.

int area = arr[x][y];

if (x0 > 0) area -= arr[x0 - 1][y];

if (y0 > 0) area -= arr[x][y0 - 1];

if (x0 > 0 && y0 > 0) area += arr[x0 - 1][y0 - 1];

if (area > mx) mx = area;

}

}

}

}

// Print result

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

}

return 0;

}