#include "soccer.h"

#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


int N;
bool E[2010][2010];

int whole() {
  vector<int> cs(N, N), ds(N, -1);
  vector<int> as(N, N), bs(N, -1);
  for (int x = 0; x < N; ++x) for (int y = 0; y < N; ++y) if (E[x][y]) {
    chmin(cs[x], y); chmax(ds[x], y);
    chmin(as[y], x); chmax(bs[y], x);
  }
  const int A = *min_element(as.begin(), as.end());
  const int B = *max_element(bs.begin(), bs.end());
  const int C = *min_element(cs.begin(), cs.end());
  const int D = *max_element(ds.begin(), ds.end());
cerr<<"["<<A<<", "<<B<<"] * ["<<C<<", "<<D<<"]"<<endl;
  
  for (int x = A; x <= B; ++x) {
    for (int y = cs[x]; y <= ds[x]; ++y) if (!E[x][y]) return 0;
  }
  for (int y = C; y <= D; ++y) {
    for (int x = as[y]; x <= bs[y]; ++x) if (!E[x][y]) return 0;
  }
  
  {
    int a0 = N, b0 = -1;
    int a1 = N, b1 = -1;
    for (int x = A; x <= B; ++x) {
      if (C == cs[x]) { chmin(a0, x); chmax(b0, x); }
      if (D == ds[x]) { chmin(a1, x); chmax(b1, x); }
    }
cerr<<"  ["<<a0<<", "<<b0<<"], ["<<a1<<", "<<b1<<"]"<<endl;
    if (!(a0 <= a1 && b1 <= b0) && !(a1 <= a0 && b0 <= b1)) return 0;
    for (int x = A; x < a0; ++x) if (!(cs[x] >= cs[x + 1])) return 0;
    for (int x = B; x > b0; --x) if (!(cs[x] >= cs[x - 1])) return 0;
    for (int x = A; x < a1; ++x) if (!(ds[x] <= ds[x + 1])) return 0;
    for (int x = B; x > b1; --x) if (!(ds[x] <= ds[x - 1])) return 0;
  }
  {
    int c0 = N, d0 = -1;
    int c1 = N, d1 = -1;
    for (int y = C; y <= D; ++y) {
      if (A == as[y]) { chmin(c0, y); chmax(d0, y); }
      if (B == bs[y]) { chmin(c1, y); chmax(d1, y); }
    }
cerr<<"  ["<<c0<<", "<<d0<<"], ["<<c1<<", "<<d1<<"]"<<endl;
    if (!(c0 <= c1 && d1 <= d0) && !(c1 <= c0 && d0 <= d1)) return 0;
    for (int y = C; y < c0; ++y) if (!(as[y] >= as[y + 1])) return 0;
    for (int y = D; y > d0; --y) if (!(as[y] >= as[y - 1])) return 0;
    for (int y = C; y < c1; ++y) if (!(bs[y] <= bs[y + 1])) return 0;
    for (int y = D; y > d1; --y) if (!(bs[y] <= bs[y - 1])) return 0;
  }
  
  int area = 0;
  for (int x = 0; x < N; ++x) for (int y = 0; y < N; ++y) if (E[x][y]) {
    ++area;
  }
  return area;
}

int biggest_stadium(int N_, std::vector<std::vector<int>> F)
{
  N = N_;
  for (int x = 0; x < N; ++x) for (int y = 0; y < N; ++y) {
    E[x][y] = !F[x][y];
  }
  return whole();
}