#include<bits/stdc++.h>
using namespace std;
void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
}
const int maxn=1e5+1;
int n,a[maxn],br;
string s;
void solve()
{
    cin>>n;
    cin>>s;
    a[0]=(int)(s[0]-'0');
    for(int i=1;i<s.size();i++)
    {
        a[i]=(int)(s[i]-'0');
        if(a[i]==0&&a[i-1]==1)
        {
            a[i]=1;
            br++;
        }
    }
    cout<<br<<endl;
}
int main()
{
    freopen("freddy.in","r",stdin);
    freopen("freddy.out","w",stdout);
    solve();

    return 0;
}