#include <bits/stdc++.h>
using namespace std;


int main() {
	int n;
	cin >> n;
	string s;
	cin >> s;
	int start=0;
	int count=0;
	while(start<=n-1){
		if(start==n-1){
			if(s[start]=='0')count++;
			break;
		}
		else if(start==n-2){
			if(s[start]=='0'&&s[start+1]=='0')count++;
			break;
		}else{
		if(s[start]=='0'){//0
			if(s[start+1]=='0'){//1
				count++;
				s[start+1]='1';
			}
			if(s[start+2]=='0'){//1
				count++;
				s[start+2]='1';
			}
			start+=2;
		}
		else{//1
			start+=1;
		}
		}
	}
	cout << count << endl;
}