#include <cstdio>
int main() {
  int n, arr[101][101] = {};
  while (scanf("%d", &n) != EOF) {
    for (int i = 1; i <= n; ++i) {
      for (int j = 1; j <= n; ++j) {
        scanf("%d", &arr[i][j]);
      }
    }
    int col_sum[101][101] = {};
    for (int i = 1; i <= n; ++i) {
      for (int j = 1; j <= n; ++j) {
        col_sum[i][j] = col_sum[i - 1][j] + arr[i][j];
      }
    }
    int ans = -128, sum;
    for (int i = 0; i <= n; ++i) {
      for (int j = i + 1; j <= n; ++j) {
        sum = 0;
        for (int row = 1; row <= n; ++row) {
          sum = sum + col_sum[j][row] - col_sum[i][row];
          if (sum > ans) ans = sum;
          if (sum < 0) sum = 0;
        }
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}