#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll

const int N = 1e5+10,mo = 1e9+7;

int a[N];




inline void solve(){
    int n;cin>>n;
    for (int i = 2; i <= n; i++)cin >> a[i];
    a[2] = 1;
    ll flag = 0, ans = 1, cnt = 0;
    for (int i = 2; i <= n; i++){
        if (a[i] == 0)cnt++;
        else {
            if (cnt){
                cnt = 0;
                flag = 1;
            }
        }
    }
    cout << max(ans + flag, cnt + ans) << endl;
}



signed main(){
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int WTN666=1;//cin>>WTN666;
    while(WTN666--){
        solve();
    }
}