#include <bits/stdc++.h>
using namespace std;
bool dp[4][2005][2005];
int biggest_stadium(int N, vector<vector<int>> F) {
for (int i=0; i<N; i++) {
for (int j=0; j<N; j++) {
bool tree = F[i][j] == 1;
bool to = i == 0 || dp[0][i-1][j];
bool le = j == 0 || dp[0][i][j-1];
dp[0][i][j] = tree && to && le;
}
}
for (int i=0; i<N; i++) {
for (int j=N-1; j>=0; j--) {
bool tree = F[i][j] == 1;
bool to = i == 0 || dp[1][i-1][j];
bool ri = j == N-1 || dp[1][i][j+1];
dp[1][i][j] = tree && to && ri;
}
}
for (int i=N-1; i>=0; i--) {
for (int j=0; j<N; j++) {
bool tree = F[i][j] == 1;
bool bo = i == N-1 || dp[2][i+1][j];
bool le = j == 0 || dp[2][i][j-1];
dp[2][i][j] = tree && bo && le;
}
}
for (int i=N-1; i>=0; i--) {
for (int j=N-1; j>=0; j--) {
bool tree = F[i][j] == 1;
bool bo = i == N-1 || dp[3][i+1][j];
bool ri = j == N-1 || dp[3][i][j+1];
dp[3][i][j] = tree && bo && ri;
}
}
bool entire = true;
int sz = 0;
for (int i=0; i<N; i++) {
for (int j=0; j<N; j++) {
bool tree = F[i][j] == 1;
if (tree && !dp[0][i][j] && !dp[1][i][j] && !dp[2][i][j] && !dp[3][i][j]) {
entire = false;
// cout << i << "," << j << "\n";
break;
}
sz += 1 - tree;
}
}
// check row intervals work
int i1 = 0, i2 = N-1;
while (i1 < i2) {
int tl = -1, tr = N;
for (int j=0; j<N; j++) {
if (dp[0][i1][j]) tl = j;
else break;
}
for (int j=N-1; j>=0; j--) {
if (dp[1][i1][j]) tr = j;
else break;
}
int bl = -1, br = N;
for (int j=0; j<N; j++) {
if (dp[2][i2][j]) bl = j;
else break;
}
for (int j=N-1; j>=0; j--) {
if (dp[3][i2][j]) br = j;
else break;
}
int l = max(bl, tl);
int r = min(br, tr);
if (l == tl && r == tr) i1++;
else if (l == bl && r == br) i2--;
else { entire = false; break; }
}
// check column intervals work
int j1 = 0, j2 = N-1;
while (j1 < j2) {
int tl = -1, bl = N;
for (int i=0; i<N; i++) {
if (dp[0][i][j1]) tl = i;
else break;
}
for (int i=N-1; i>=0; i--) {
if (dp[2][i][j1]) bl = i;
else break;
}
int tr = -1, br = N;
for (int i=0; i<N; i++) {
if (dp[1][i][j2]) tr = i;
else break;
}
for (int i=N-1; i>=0; i--) {
if (dp[3][i][j2]) br = i;
else break;
}
int t = max(tl, tr);
int b = min(bl, br);
if (t == tr && b == br) j1++;
else if (t == tl && b == bl) j2--;
else { entire = false; break; }
}
if (entire) {
return sz;
} else {
return 0;
}
}
