//Make CSP great again
//Vengeance
#include <bits/stdc++.h>
#define TASK "TESTCODE"
using namespace std;
const int N = 2e5;
int n, k, m;
int a[N + 1];
void read()
{
    cin >> n >> k >> m;
    for (int i = 1; i <= n; ++ i)
    {
        cin >> a[i];
        a[i] -= m;
    }
}
void solve()
{
    string s;
    cin >> s;
    int n = s.size();
    int pf = 0;
    int res = n;
    for (int x = 0; x < n; x++) {
        for (int y = x - 1; y < n; y++) {
            int cur = pf;
            for (int i = y + 1; i < n; i++) cur += s[i] == '1';
            for (int i = x; i <= y; i++) cur += s[i] == '0';
            res = min(res, cur);
        }
        pf += s[x] == '1';
    }
    cout << res << "\n";
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
    }
    int t = 1;
    bool typetest = false;
    if (typetest)
    {
        cin >> t;
    }
    for (int __ = 1; __ <= t; ++ __)
    {
        //cout << "Case " << __ << ": ";
//        read();
        solve();
    }
}