#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <array>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
#include <memory>
#include <regex>
using namespace std;

int main()
{
    string s;
    cin >> s;
    s = '0' + s;

    int i = s.size() - 1;
    int ans = 0;
    while(i >= 0){
        if(s[i] == '0'){
            -- i;
        }
        else if(i == 0 || s[i-1] == '0'){
            s[i] = '0';
            -- i;
            ++ ans;
        }
        else{
            while(s[i] == '1'){
                s[i] = '0';
                -- i;
            }
            s[i] = '1';
            ++ ans;
        }
    }
    cout << ans << endl;

    return 0;
}