// https://www.youtube.com/watch?v=wthasN45KuY
// You said I’d fly away
// But my walls have kept me down
// Now I’m lost and I’m afraid
// And I’m close to hit the ground
// 
// You said I’d fly away
// You said I’d fly anywhere
// But I keep on Falling

#ifndef ONLINE_JUDGE
#include "templates/debug.hpp"
#else
#define debug(...)
#endif

#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using u64 = uint64_t;

#define int i64
constexpr int INF = 0x3f3f3f3f;
void solve() {
    string s; cin >> s;
    int n = s.size();
    vector dp(n + 1, vector<int>(3, INF));
    dp[0][0] = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] == '0') {
            dp[i + 1][0] = dp[i][0];
            dp[i + 1][1] = dp[i][1] + 1;
            dp[i + 1][2] = min(dp[i][1], dp[i][2]);
        } else {
            dp[i + 1][0] = dp[i][0] + 1;
            dp[i + 1][1] = min(dp[i][0], dp[i][1]);
            dp[i + 1][2] = dp[i][2] + 1;
        }
    }
    cout << ranges::min(dp[n]) << '\n';
}
#undef int

// Make bold hypotheses and verify carefully
int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}