#include <bits/stdc++.h> 
using namespace std;
#include <stdio.h>
#include <iomanip>
#include <iostream>
#include <string>
#include <algorithm>

int main(){
  string a;
  cin >> a;
  int b = count(a.cbegin(),a.cend(),'0');
  cout << (a.size()-1)-b; 
}