#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define vi vector <int>
#define sz(a) ((int) (a).size())
#define me(f, x) memset(f, x, sizeof(f))
#define ull unsigned long long
#define pb emplace_back
using namespace std; 
const int N = 1e6 + 7;
string s;
int main() {
	// freopen("data.txt","r",stdin);
	ios :: sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int ans = 1e9;
	cin >> s;
	L(l, 0, sz(s) - 1) {
		L(r, l - 1, sz(s) - 1) {
			int cnt = 0;
			L(j, l, r) {
				cnt += s[j] == '0';
			}
			L(j, 0, l - 1)
				cnt += s[j] == '1';
			L(j, r + 1, sz(s) - 1)
				cnt += s[j] == '1';
			ans = min(ans, cnt);
		}
	}
	cout << ans << '\n';
	return 0;
}