#include "bits/stdc++.h"
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;

using ll = long long;
const ll MOD = 1e9 + 7;

int main() {
    string N;
    cin >> N;
    int ans = 0;
    for (int i = N.size() - 1; i >= 0; i--) {
        if (N[i] == '0') continue;
        if (i == 0) {
            ans++;
            break;
        }
        if (N[i - 1] == '0') {
            ans++;
            continue;
        }
        ans++;
        while (N[i - 1] == '1' && i > 0) {
            i--;
        }
        if (i > 0) N[i - 1] = '1';
        else ans++;
    }
    cout << ans << endl;
}