// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;
// mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const int mod = 998244353;
const int N = 1e5 + 5;
string s;
int dp[N][3];
void MAIN() {
    cin >> s;
    int n = (int)s.size();
    s = '$' + s;
    for (int i = 1; i < (int)s.size(); ++i) {
        if (s[i] == '1') {
            dp[i][0] = dp[i - 1][0] + 1;
            dp[i][1] = min(dp[i - 1][1], dp[i - 1][0]);
            dp[i][2] = dp[i - 1][2] + 1;
        } else {
            dp[i][0] = dp[i - 1][0];
            dp[i][1] = dp[i - 1][1] + 1;
            dp[i][2] = min(dp[i - 1][2], dp[i - 1][1]);
        }
    }
    int ans = min({dp[n][0], dp[n][1],dp[n][2]});
    cout << ans << endl;
}

int main() {
#ifdef LOCAL
    auto start = chrono::steady_clock::now();
    freopen("miku.in", "r", stdin);
    freopen("miku.out", "w", stdout);
#endif
    ios::sync_with_stdio(0);
    cin.tie(0);
    int T = 1;
    // cin >> T;
    while (T--) MAIN();
#ifdef LOCAL
    auto end = chrono::steady_clock::now();
    cout << "\nqwq: " << chrono::duration_cast<chrono::milliseconds>(end - start).count() << "ms\n";
#endif
    return 0;
}