#include <bits/stdc++.h>

#include "soccer.h"

#if defined(LOCAL)
#define DBG_MACRO_NO_WARNING
#include <dbg.hpp>

#include "grader.cpp"
#else
#define dbg(x...) (0)
#endif

using namespace std;

using ll = long long;

// #define int ll
#define rep(i, f, t) for (int i = (f), ed##i = (t); i <= ed##i; ++i)
#define re(i, t) rep (i, 1, t)
#define per(i, t, f) for (int i = (t), ed##i = (f); i >= ed##i; --i)
#define ste(i, f, t, s) for (int i = (f), ed##i = (t); i <= ed##i; i += s)
#define nxt(i, f, g) for (int i = g.h[f]; i; i = g.e[i].n)
#define umod(x) ((x) >= mo && ((x) -= mo))
#define dmod(x) ((x) < 0 && ((x) += mo))
#define y1 y1__
#define fio(x) (freopen(x ".in", "r", stdin), freopen(x ".out", "w", stdout))

template <class T, class E>
__attribute__((always_inline)) inline void up(T &x, E &&y) {
  if (x < y) x = y;
}
template <class T, class E>
__attribute__((always_inline)) inline void down(T &x, E &&y) {
  if (y < x) x = y;
}

namespace qingwa {
const int N = 2009;
const int inf = 1e9 + 7;
int n, a[N][N], dp[2][N][N][2], mx[2][N][N][2];

inline int Main() {
  re (i, n)
    re (j, n) a[i][j] += a[i][j - 1];
  int ans = 0;
  re (i, n) {
    int t = i & 1;
    re (l, n)
      rep (r, l, n) {
        dp[t][l][r][0] = mx[!t][l][r][0] + ((a[i][r] - a[i][l - 1]) ? -inf : r - l + 1);
        dp[t][l][r][1] = mx[!t][l][r][1] + ((a[i][r] - a[i][l - 1]) ? -inf : r - l + 1);
        up(ans, dp[t][l][r][0]);
        up(ans, dp[t][l][r][1]);
      }
    re (len, n)
      re (l, n) {
        int r = l + len - 1;
        if (r > n) break;
        mx[t][l][r][0] = max({mx[t][l + 1][r][0], mx[t][l][r - 1][0], dp[t][l][r][0]});
      }
    per (len, n, 1)
      re (l, n) {
        int r = l + len - 1;
        if (r > n) break;
        mx[t][l][r][1] =
            max({mx[t][l - 1][r][1], mx[t][l][r + 1][1], dp[t][l][r][0], dp[t][l][r][1]});
      }
  }
  return ans;
}
}  // namespace qingwa

int biggest_stadium(int N, std::vector<std::vector<int>> F) {
  using namespace qingwa;
  n = N;
  rep (i, 0, n - 1)
    rep (j, 0, n - 1) a[i + 1][j + 1] = F[i][j];
  return qingwa::Main();
}