#include <bits/stdc++.h>
using namespace std;
template<class T> bool chmin(T& a, T b) { return a > b ? a = b, true : false; }
template<class T> bool chmax(T& a, T b) { return a < b ? a = b, true : false; }
template<typename T>
concept Iterable = requires(T t) { std::begin(t); std::end(t); };
template<typename T>
	requires Iterable<T> && (!is_same_v<T, string>)
ostream& operator<<(ostream& os, const T& container) { for (auto& element : container) os << element << ' '; return os; }
template<typename R>
	requires ranges::range<R> && (!is_same_v<decay_t<R>, string>) && (!is_same_v<decay_t<R>, const char*>)
ostream& operator<<(ostream& os, R&& range) { for (auto& element : range)os << element << ' '; return os; }
template<typename T>
	requires Iterable<T> && (!is_same_v<T, string>)
istream& operator>>(std::istream& is, T& container) { for (auto& e : container)is >> e; return is; }
using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
template<class T = ll> struct Edge {
	int to;
	T weight;
	bool operator==(Edge e) { return this->to == e.to and this->weight == e.weight; }
	bool operator<(Edge e) { return this->to == e.to ? this->weight < e.weight : this->to < e.to; }
};
#ifdef _DEBUG
#define SHOW(n) {const auto& _ret = n; cerr << #n << ": " << _ret << endl;}
#define MSG(x) cerr << x << endl;
#else
#define SHOW(n)
#define MSG(x)
#endif

//AtCoder Library
#include <atcoder/all>
using namespace atcoder;
//using mint = modint998244353;
using mint = modint1000000007;
//using mint1 = dynamic_modint<0>;
//using mint = modint;
//mint::set_mod();
istream& operator>>(istream& is, mint& x) { ll r; is >> r; x = r; return is; }
ostream& operator<<(ostream& os, mint& x) { os << x.val(); return os; }

//boost
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision;
//using l3 = int128_t;


int main() {
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int n;
	string s;
	cin >> n >> s;

	if (n == 1) {
		if (s[0] == '0')cout << 1 << endl;
		else cout << 0 << endl;
		return 0;
	}

	int res = 0;
	for (int i = 1; i < n; ++i) {
		if (i - 2 >= 0 and s[i - 2] == '0' and s[i - 1] == '1' and s[i] == '0') {
			++res;
			s[i] = '1';
		}
		else if (s[i - 1] == '0' and s[i] == '0') {
			++res;
			s[i] = '1';
		}
	}

	cout << res << endl;


	return 0;
}