#include <bits/stdc++.h>
using namespace std;
#define fastio (ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL))
typedef long long ll;
typedef long double lld;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
const int MAXSIZE = 2000000;
const long long INF = 1e18 + 5;
const double EPSILON = 1e-14;
const ll DIV = 2000003;
const long double pi = 3.14159265358979323846264338327950288419716939937510L;

int n;
int arr[101010];

int main()
{
    fastio;
    int ans = 1;
    cin >> n;
    int cur = 0;
    for (int i = 1; i < n; i++)
    {
        cin >> arr[i];
        if (n > 3 && arr[i] == 0 && i > 1)
            ans = 2;
    }
    int mx = 0;
    int con = 0;
    for (int i = 1; i < n; i++)
    {
        if (arr[i] == 0)
        {
            con++;
        }
        else
            con = 0;
    }
    if (con == n - 1)
        con--;
    if (n > 2)
        ans = max(ans, con + 1);

    cout << ans;
    return 0;
}