#include"bits/stdc++.h"
//#include<boost/multi_array.hpp>
//#include<boost/optional.hpp>
//#include<boost/range/irange.hpp>
//#include<boost/range/algorithm.hpp>
//#include<boost/range/adaptors.hpp>

using namespace std;
//namespace adaptor = boost::adaptors;

#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int, int>;

#include<bits/stdc++.h>
using namespace std;

//int mod = 1000000007;

void Main()
{
    string c;
    cin >> c;
    int zerocou = 0;
    rep(i, c.size()){
        if(c[i] == '0'){
            zerocou++;
        }
    }
    cout << c.size() -1 -zerocou << endl;
}

int main()
{
	std::cin.tie(nullptr);
	std::ios_base::sync_with_stdio(false);
	std::cout << std::fixed << std::setprecision(15);
	Main();
	return 0;
}