# include <bits/stdc++.h>
using namespace std;
const int maxn = 100005;
int a[maxn],b[maxn];
bool fl[maxn];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
freopen("freddy.in","r",stdin);
freopen("freddy.out","w",stdout);
    int n;
    cin>>n;
    int i,j;
    char ch;
    int num = 0;
    for(i = 1;i<=n;i++)
    {
        cin>>ch;
        fl[i] = ch-'0';
        if(fl[i])
        {
           if(i==1 || !fl[i-1])
           {
               num++;
           }
        }
        a[i] = num;
    }
    num = 0;
    for(i = n;i>=1;i--)
    {
        if(!fl[i])
        {
            if(i==n || fl[i+1])
            {
                num++;
            }
        }
        b[i] = num;
    }
    int ans = 1e9;
    for(i = 0;i<=n;i++)
    {
        ans = min(ans,a[i]+b[i+1]);
        //cout<<i<<" "<<a[i]<<" "<<b[i+1]<<endl;
    }
    cout<<ans<<endl;
return 0;
}