#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3")
#include <bits/stdc++.h>

#define el '\n'
#define F first
#define S second

typedef long long ll;
typedef long double ld;
typedef __int128 bigInt;

using namespace std;

const int N = 5e5 + 5, INF = 1e9 + 5, mod = 1e9 + 7, LOG = 21, SQ = 500;



void doWork() {
    int n;
    cin >> n;

    bool buffer = 0;
    int ans = 1;

    bool x;
    cin >> x;

    for (int i = 0; i < n - 2; i++) {
        cin >> x;
        if (x) {
            ans = min(ans, 2);
            buffer = 1;
        }
        else {
            if (buffer) {
                buffer = 0;
                ans = max(ans, 2);
            }
            else {
                ans++;
            }
        }
    }

    cout << ans << el;
}

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

    int tests = 1;
//    cin >> tests;
    for (int i = 1; i <= tests; i++) {
        doWork();
    }
}