#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<=(b);++i)

using namespace std;

const int N = 100;
char str[N];

signed main() {
    cin >> (str + 1);
    int n = strlen(str + 1);
    int ret = n;
    rep(l,1,n) rep(r,l,n) {
        int ans = 0;
        rep(i,1,l-1) if(str[i] == '1') ++ ans;
        rep(i,r+1,n) if(str[i] == '1') ++ ans;
        rep(i,l,r) if(str[i] == '0') ++ ans;
        ret = min(ret, ans);
    }
    cout << ret << endl;
    return 0;
}