#include<bits/stdc++.h>
using namespace std;
const int N = 2000 + 5;
int n, pref[N][N], l[N][N], r[N][N], u[N][N], d[N][N], f[N][N];
void precompute()
{
for(int i = 0; i < n; i ++)
for(int j = 0; j < n; j++)
l[i][j] = r[i][j] = u[i][j] = d[i][j] = 1 - f[i][j] ;
for(int i = 0; i < n; i ++)
for(int j = 1; j < n; j ++)
if(l[i][j])
l[i][j] += l[i][j - 1];
for(int i = 0; i < n; i ++)
for(int j = n - 2; j >= 0; j --)
if(r[i][j])
r[i][j] += r[i][j + 1];
for(int i = 1; i < n; i ++)
for(int j = 0; j < n; j ++)
if(u[i][j])
u[i][j] += u[i - 1][j];
for(int i = n - 2; i >= 0; i --)
for(int j = 0; j < n; j ++)
if(d[i][j])
d[i][j] += d[i + 1][j];
for(int i = 0; i < n; i ++)
for(int j = 0; j < n; j ++)
pref[i + 1][j + 1] = pref[i + 1][j] + pref[i][j + 1] - pref[i][j] + f[i][j];
}
int extract(int idx)
{
vector<int> a, b;
for(int i = 0; i < n; i++)
a.push_back(u[idx][i]), b.push_back(d[idx][i] - 1);
int fans = 0;
for(int p = 0; p < n; p ++)
{
int ans = a[p] + b[p];
int x1 = a[p], x2 = b[p];
for(int j = p - 1; j >= 0; j --)
{
x1 = min(x1, a[j]);
x2 = min(x2, b[j]);
ans += x1 + x2;
}
x1 = a[p], x2 = b[p];
for(int j = p + 1; j < n; j++)
{
x1 = min(x1, a[j]);
x2 = min(x2, b[j]);
ans += x1 + x2;
}
fans = max(fans, ans);
}
return fans;
}
int biggest_stadium(int N, vector<vector<int> > F)
{
n = N;
for(int i = 0; i < n; i ++)
for(int j = 0; j < n; j ++)
f[i][j] = F[i][j];
precompute();
int ans = 0;
for(int i = 0; i < n; i ++)
ans = max(ans, extract(i));
return ans;
}
