#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
const int mod = 998244353, N = 100007;

int main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int n;
	cin >> n, --n;
	vector <int> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	int ans = 1;
	vector <int> lst(n, -1);
	for (int i = n - 1; ~i; --i) {
		if (i + 1 < n) {
			lst[i] = lst[i + 1];
		}
		if (a[i] == 1) {
			lst[i] = i;
		}
	}
	int prev = -1;
	for (int i = 0; i < n; ++i) {
		if (a[i] == 0) {
			int closet = i + 1;
			if (prev != -1) closet = min(closet, i - prev + 1);
			if (lst[i] != -1) closet = min(closet, lst[i] - i + 1);
			ans = max(ans, closet);
		} else {
			prev = i;
		}
	}
	cout << ans << '\n';
}