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


int main() {
    string s;
    while (cin >> s) {
        while (!s.empty() && ~s.back() & 1) s.pop_back();
        reverse(s.begin(), s.end());
        while (!s.empty() && ~s.back() & 1) s.pop_back();
        if (!s.empty()) {
            int n = s.size();
            vector<int> pre(n + 1);
            for (int i = 0; i < n; i++) {
                pre[i + 1] = pre[i] + (s[i] & 1);
            }
            int res = min(pre[n], n - pre[n]);
            for (int i = 1; i < n; i++) {
                res = min(res, pre[i] + (n - i - (pre[n] - pre[i])));
                res = min(res, (i - pre[i]) + (pre[n] - pre[i]));
            }
            cout << res << '\n';
        } else {
            cout << 0 << '\n';
        }
    }

    return 0;
}