#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); i++)
#define R(i, j, k) for(int i = (j); i >= (k); i--)
#define ll long long
#define ull unsigned long long 
#define sz(a) ((int) a.size())
#define vi vector<int>
#define me(a, x) memset(a, x, sizeof(a))
using namespace std;
const int N = 2007;

int n;
int lst[N][N];
map < pair < int, int >, int > f[N][N]; 

void chk(int &x, int y) {
	if(y > x) x = y;
}

int up[N][N], dw[N][N], tms;
const int block = 16, blen = N / block + 5;
struct rmq{
	int bcnt, lg[blen];
	int s[10][blen];
	int sb[N];
	int a[N], suf[N], pre[N];
	
	int stk[block + 3], tp;
	inline int qry(int l, int r) {
		int bl = l / block;
		int br = r / block;
		if(bl == br) {
			return *max_element(a + l, a + r + 1);
//			 a[l + __builtin_ctz(sb[r] >> (l - bl * block))];
		}
		int ans = max(suf[l], pre[r]);
		++bl, --br;
		if(bl <= br) {
			int p = lg[br - bl + 1];
			ans = max(ans, max(s[p][bl], s[p][br - (1 << p) + 1]));
		}
		return ans;
	}
	void init() { 
		for(int l = 0, r; l < n; l = r + 1) {
			r = min(l + block - 1, n - 1);
			L(i, l, r) pre[i] = suf[i] = a[i];
			L(i, l + 1, r) pre[i] = max(pre[i], pre[i - 1]);
			R(i, r - 1, l) suf[i] = max(suf[i], suf[i + 1]);
			s[0][bcnt++] = pre[r];
			tp = 0;
			int cur = 0;
			L(i, 0, r - l) {
				while(tp && a[stk[tp] + l] < a[i + l]) 
					cur -= 1 << stk[tp], --tp;
				stk[++tp] = i, cur += 1 << i, sb[i] = cur;
			}
		}
		L(i, 2, bcnt) lg[i] = lg[i >> 1] + 1;
		L(i, 1, lg[bcnt]) 
			L(j, 0, bcnt - (1 << i) + 1) 
				s[i][j] = max(s[i - 1][j], s[i - 1][j + (1 << (i - 1))]);
	}
} U[N], D[N];

void pb(int nl, int nr, int tl, int tr, int ans) {
	++tms;
	if(tms > 6e7) {
		assert(false);
	}
	int clen = nr - nl; 
	nl = U[nl].qry(tl, tr); 
	nr = -D[nr].qry(tl, tr);
	chk(f[nl][nr][make_pair(tl, tr)], ans + (nr - nl - clen) * (tr - tl + 1));
}

int biggest_stadium(int N, vector < vi > F) {
	n = N;
	L(i, 0, N - 1) {
		int l = 0;
		L(j, 0, N) {
			if(j == N || F[i][j] == 1) l = j + 1;
			if(j < N) lst[i][j] = l;
		}
	}
	L(i, 0, N - 1) {
		L(j, 0, N - 1) {
			if(F[i][j] == 1) up[i][j] = i + 1;
			else up[i][j] = i == 0 ? i : up[i - 1][j];
			U[i].a[j] = up[i][j];
		}
		U[i].init();
	}
	R(i, N - 1, 0) {
		L(j, 0, N - 1) {
			if(F[i][j] == 1) dw[i][j] = i - 1;
			else dw[i][j] = i == N - 1 ? i : dw[i + 1][j];
			D[i].a[j] = -dw[i][j];
		}
		D[i].init();
	}
	
	L(i, 0, N - 1) {
		int l = 0;
		L(j, 0, N) {
			if(j == N || F[i][j] == 1) {
				if(l < j) pb(i, i, l, j - 1, j - l);
				l = j + 1;
			}
		}
	}
	
	int ans = 0;
	L(len, 1, N) {
		L(l, 0, N - len) {
			int r = l + len - 1;
			for(auto &o : f[l][r]) {
				ans = max(ans, o.second);
				int tl = o.first.first;
				int tr = o.first.second;
				
				int nl = l;
				int nr = r;
				while(nl > 0 && lst[nl - 1][tr] <= tl) --nl;
				while(nr < N - 1 && lst[nr + 1][tr] <= tl) ++nr;
				
				if(nl != l || nr != r) {
					chk(f[nl][nr][make_pair(tl, tr)], 
						o.second + ((nr - nl) - (r - l)) * (tr - tl + 1));
					continue;
				}
				
				if(nl > 0) {
					for(int r = tr, l; r >= tl; r = l - 2) {
						l = max(tl, lst[nl - 1][r]);
						if(l > r) continue;
						pb(nl - 1, nr, l, r, o.second + r - l + 1);
					}
				}
				
				if(nr < N - 1) {
					for(int r = tr, l; r >= tl; r = l - 2) {
						l = max(tl, lst[nr + 1][r]);
						if(l > r) continue;
						pb(nl, nr + 1, l, r, o.second + r - l + 1);
					}
				}
			}
		}
	}
	return ans;
}

//int main() {
//	cout << biggest_stadium(5, {vi{0, 0, 0, 0, 0}, 
// vi{1, 0, 0, 0, 0}, 
// vi{0, 0, 0, 0, 0}, 
// vi{0, 0, 0, 0, 0}, 
// vi{0, 0, 1, 0, 0}});
//}