#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define ll long long
#define pb push_back
#define ALL(x) (x).begin(), (x).end()
#define GETBIT(mask, i) ((mask) >> (i) & 1)
#define MASK(i) ((1LL) << (i))
#define SZ(x) ((int)(x).size())
#define CNTBIT(mask) __builtin_popcount(mask)
template<class X, class Y> bool maximize(X &x, Y y){ if (x < y) {x = y; return true;} return false;};
template<class X, class Y> bool minimize(X &x, Y y){ if (x > y) {x = y; return true;} return false;};
typedef pair<int, int> ii;
const int N = 2e5 + 5;
const int INF = 1e9 + 7;
string s;
int n;
int cnt[2][55];
void read() {
    cin >> s;
    n = SZ(s);
    s = ' ' + s;
}
int sum(int t, int l, int r) {
    if (l > r) return 0;
    return cnt[t][r] - cnt[t][l - 1];
}
void solve() {
    for(int i = 1; i <= n; i++) {
        cnt[0][i] = cnt[0][i - 1] + (s[i] == '0');
        cnt[1][i] = cnt[1][i - 1] + (s[i] == '1');
    }
    int ans = INF;
    for(int i = 1; i <= n; i++) {
        for(int j = i; j <= n; j++) {
            if (s[i] == '1' && s[j] == '1') {
                ans = min(ans, sum(0, i, j) + sum(1, 1, i - 1) + sum(1, j + 1, n));
            }
        }
    }
    if (ans == INF) ans = 0;
    cout << ans;
}
signed main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen("long.inp", "r")) {
        freopen("long.inp", "r", stdin);
        freopen("long.out", "w", stdout);
    }
    int test = 1;
    //cin >> test;
    while(test--) {
        read();
        solve();
    }
    return 0;
}