#include <iostream>
#include <algorithm>
using namespace std;
int main(){
    string s;cin>>s;
    reverse(s.begin(),s.end());
    int ans = 0;
    for(int i = 0; s.size()-1 > i; i++){
        if(s[i] == '0')continue;
        if(s[i] == '1' && s[i+1] == '0'){
            //cout << i << endl;
            ans++;
            s[i] = '0';
        }else{
            //cout << "!" << i << endl;
            int z = i+1;
            for(; s[z] == '1' && s.size() > z;z++){
                s[z] = '0';
            }
            ans++;
            if(s.size() == z){
                cout << ans+1 << endl;
                return 0;
            }
            s[z] = '1';
            i = z-1;
        }
    }
    cout << ans+(s[s.size()-1]=='1'?1:0) << endl;
}