#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	string s; cin >> s;
	vector dp(n, vector<int>(3, INF));
	// *0
	// 01
	// 11
	if (s[0] == '0') {
		dp[0][0] = 0;
		dp[0][2] = 1;
	}
	else {
		dp[0][0] = 1;
		dp[0][2] = 0;
	}
	rep2(i, 1, n) {
		if (s[i] == '0') {
			chmin(dp[i][0], dp[i - 1][2]);
			chmin(dp[i][1], dp[i - 1][0] + 1);
			chmin(dp[i][2], dp[i - 1][1] + 1);
			chmin(dp[i][2], dp[i - 1][2] + 1);
		}
		else {
			chmin(dp[i][0], dp[i - 1][2] + 1);
			chmin(dp[i][1], dp[i - 1][0] + 0);
			chmin(dp[i][2], dp[i - 1][1] + 0);
			chmin(dp[i][2], dp[i - 1][2] + 0);
		}
	}
	int ans = n;
	rep(i, 3)chmin(ans, dp[n - 1][i]);
	cout << ans << endl;
	return 0;
}