#include <bits/stdc++.h>
#define int long long
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
using namespace std;

void solve();

signed main(){
    fast
    int t = 1;
//    cin >> t;
    while(t--) solve();
}

const int N = 100;

int n;
char s[N];

void solve(){
    cin >> s;
    n = strlen(s);
    int res = 2e9;
    if(count(s, s + n, '0') == n){
        cout << 0 << '\n';
        return;
    }
    for(int i = 0; i < n; i++){
        for(int j = i; j < n; j++){
            int cnt = 0;
            for(int l = 0; l < i; l++){
                cnt += s[l] == '1';
            }
            for(int r = j + 1; r < n; r++){
                cnt += s[r] == '1';
            }
            for(int l = i; l <= j; l++){
                cnt += s[l] == '0';
            }
            res = min(res, cnt);
        }
    }
    cout << res << '\n';
}