#include <bits/stdc++.h>
using namespace std;
int main(){
    string s;
    cin >> s;
    int n = s.size(), ans = 0, c = 0;
    for(int i = 0; i <= n; i++){
        int b = (i < n ? s[n - 1 - i] - '0' : 0);
        int t = b + c;
        if(t & 1){
            ans++;
            c = (i + 1 < n && s[n - 2 - i] == '1') ? 1 : 0;
        }else{
            c = t >> 1;
        }
    }
    cout << ans << endl;
    return 0;
}