#pragma GCC optimize("Ofast")

#include <bits/stdc++.h>

#define LL long long int
#define ULL unsigned LL
#define LD long double
#define FI first
#define SE second
#define PB push_back
#define PF push_front
#define V vector
#define PQ priority_queue
#define ALL(x) x.begin(), x.end()
#define SZ(x) (int)(x).size()
#define FORI(i, a, b) for(int i = a; i < b ; ++i)
#define FORD(i, a, b) for(int i = a; i > b ; --i)

using namespace std;
using pii = pair<int, int>;

int main(){
    ifstream cin("freddy.in");
    ofstream cout("freddy.out");
//    ios_base::sync_with_stdio(false);
//    cin.tie(NULL);
//    cout.tie(NULL);
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    clock_t start_t = clock();

    int n;
    string a;
    cin >> n >> a;
    V<int> c(1, a[0] - '0');
    FORI(i,1,n){
        if (a[i] - '0' != c[c.size()-1]){
            c.push_back(a[i] - '0');
        }
    }
    n = c.size();
    V<int> pref(n+1, 0);
    FORI(i,0,n){
        pref[i+1] = pref[i] + c[i];
//        cout << pref[i+1] << ' ';
    }
    int ans = n;
    FORI(i,0,n){
        ans = min(ans, pref[i] + n - i - pref[n] + pref[i]);
    }
    cout << ans;

    return 0;
}