#include <bits/stdc++.h>
using namespace std;
bool a[1000005];

int main() {
	long long n;
	cin >> n;
	for (long long i = 0; i < n; i++) {
		cin >> a[i];
	}
	long long cnt = 1;
	long long i = 0,i_=0;
	while (1) {
		for (; i < n; i++) {
			if (i == n - 1 && a[i] == 0) {
				cout << cnt;
				return 0;
			}
			if (a[i] != 0&&i!=i_) {
				i--;
				break;
			}
		}
        i_=i;
		for (long long i = 0; i < n; i++) {
			if (a[i] == 0) {
				a[i] = 1;
			} else {
				a[i] = 0;
			}
		}
        cnt++;
	}
	return 0;
}