#include <bits/stdc++.h>
#define F first
#define S second

using namespace std;

int n;
int arr[1000005];
int dp[1000005] = {0};
const int N = 1e6 + 5;

signed main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int mx = 0;
    cin >> n;
    int get0 = 0;
    for (int i = 2; i <= n; i++) {
        cin >> arr[i];
        if (i == 2) {
            dp[i] = 1;
        } else if (arr[i] || arr[i - 1]) {
            dp[i] = 2;
        } else {
            dp[i] = max(dp[i - 1] + 1, dp[i]);
        }
        if (arr[i] == 0)
            get0 = 1;
        else
            dp[i] = 1;
    }
    cout << dp[n];
    return 0;
}