#include <bits/stdc++.h>

#define MAXN 100005
#define endl '\n'

using namespace std;

int splits[MAXN];

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    freopen("freddy.in","r",stdin);
    freopen("freddy.out","w",stdout);

    int n; cin >> n;
    string s; cin >> s;

    bool one = false;
    for (char c: s) one |= (c - '0');

    if (!one) {
        cout << 0 << endl;
        return 0;
    }

    int ans = INT_MAX;

    int cnt0 = 0;
    for (int i = n - 1; i >= 0; i--) {
        splits[i] = splits[i + 1];
        if (s[i] == '1') continue;

        if (i == 0 || s[i - 1] == '1') cnt0++;
        splits[i] = cnt0;
    }

    int cnt1 = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] == '0') continue;
        if (i == n - 1 || s[i + 1] == '0') {
            cnt1++;
            ans = min(ans, cnt1 - 1 + splits[i + 1]);
        }
    }

    cout << ans << endl;

    return 0;
}