#include <bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define SIZE(x) (int)x.size()
#define forsn(i,s,n) for(int i=int(s);i<int(n);i++)
#define forn(i,n) for(int i=0;i<int(n);i++)
#define dforsn(i,s,n) for(int i=int(n)-1;i>=int(s);i--)
#define dforn(i,n) for(int i=int(n)-1;i>=0;i--)
#define fst first
#define snd second
typedef pair<int,int> ii;
const int MAXN = 500;
int f[MAXN][MAXN];
int dp[MAXN][MAXN];
ii ran[MAXN][MAXN];
int L[MAXN][MAXN], R[MAXN][MAXN];
int n;
pair<int,ii> solve(int l, int r, int p) {
if(l>r) return {0LL,{-1,n}};
if(dp[l][r]!=-1) return {dp[l][r],ran[l][r]};
auto calculate = [&](pair<int,ii> prev, int i) {
auto [val,range] = prev;
int mini = max(range.fst, L[i][p]), maxi = min(range.snd, R[i][p]);
return (pair<int,ii>){val+max(maxi-mini-1,0),{mini,maxi}};
};
pair<int,ii> res = max(calculate(solve(l+1,r,p),l),
calculate(solve(l,r-1,p),r));
dp[l][r]=res.fst, ran[l][r]=res.snd;
return res;
}
int only_check(vector<vector<int>> f) {
forn(i,n) {
int prev=1, count=0;
forn(j,n) {
if(f[i][j]!=prev) count++;
prev=f[i][j];
}
if(prev!=1) count++;
if(count!=2 && count!=0) return -1;
}
forn(j,n) {
int prev=1, count=0;
forn(i,n) {
if(f[i][j]!=prev) count++;
prev=f[i][j];
}
if(prev!=1) count++;
if(count!=2 && count!=0) return -1;
}
vector<int> l(n,0), r(n,n);
forn(i,n) forn(j,n) {
if(f[i][j]==0) {
l[i]=j;
break;
}
}
forn(i,n) dforn(j,n) {
if(f[i][j]==0) {
r[i]=j;
break;
}
}
bool flag=false;
forn(i,n-1) {
if(l[i]<l[i+1]) flag=true;
if(l[i]>l[i+1] && flag) return -1;
}
flag=false;
forn(i,n-1) {
if(r[i]>r[i+1]) flag=true;
if(r[i]<r[i+1] && flag) return -1;
}
int count=0;
forn(i,n) forn(j,n) {
count += f[i][j]==0;
}
return count;
}
int biggest_stadium(int N, vector<vector<int>> F) {
n=N;
if(n>500) return only_check(F);
forn(i,n) forn(j,n) {
f[i][j]=F[i][j];
}
forn(i,n) {
int k=-1;
forn(j,n) {
if(f[i][j]==1) k=j;
L[i][j]=k;
}
}
forn(i,n) {
int k=n;
dforn(j,n) {
if(f[i][j]==1) k=j;
R[i][j]=k;
}
}
int ans=0;
forn(i,n) {
memset(dp,-1,sizeof dp);
ans=max(ans,solve(0,n-1,i).fst);
}
return ans;
}
