#include "soccer.h"
#include<bits/stdc++.h>

using namespace std;

typedef int ll;

ll biggest_stadium(ll n, vector<vector<ll>> f) {
	map<tuple<bool, ll, ll, vector<pair<ll, ll>>>, ll> dp;
	dp[make_tuple(false, n + 1, -1, vector<pair<ll, ll>>(0))] = 0;
	for (ll i = 0; i < n; i++) {
		map<tuple<bool, ll, ll, vector<pair<ll, ll>>>, ll> ndp;
		vector<pair<ll, ll>> segs;
		segs.emplace_back(n + 1, -1);
		for (ll j = 0; j < n; j++) {
			for (ll k = j; k < n; k++) {
				if (f[i][k] == 1) {
					break;
				}
				segs.emplace_back(j, k);
			}
		}
		for (auto[l, r] : segs) {
			for (auto[x, c] : dp) {
				auto[isu, nl, nr, otrs] = x;
				if (r < nr || l > nl) {
					isu = true;
				}
				if (isu) {
					if (r > nr || l < nl) {
						continue;
					}
				}
				if (r != -1) {
					while (!otrs.empty() && otrs.back().first <= l && r <= otrs.back().second) {
						otrs.pop_back();
					}
					if (!otrs.empty() && (otrs.back().first < l || r < otrs.back().second)) {
						continue;
					}
					otrs.emplace_back(l, r);
				}
				nl = l;
				nr = r;
				ndp[make_tuple(isu, nl, nr, otrs)] = max(ndp[make_tuple(isu, nl, nr, otrs)], c + max(0, (r - l + 1)));
			}
		}
		dp = ndp;
	}
	ll ans = 0;
	for (auto[_, na] : dp) {
		if (na > ans) {
			ans = na;
		}
	}
	return ans;
}

#ifdef LOCAL
int main()
{
    int N;
    assert(1 == scanf("%d", &N));
    std::vector<std::vector<int>> F(N, std::vector<int>(N));
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < N; j++)
        {
            assert(1 == scanf("%d", &F[i][j]));
        }
    }
    fclose(stdin);

    int res = biggest_stadium(N, F);

    printf("%d\n", res);
    fclose(stdout);
    return 0;
}
#endif