// yukicoder No.1070
#include <bits/stdc++.h>
using namespace std;

int main()
{
  string s; cin >> s;

  int lim = s.size();
  int z_counter = 0;
  for(int i = 0; i < lim; ++i) {
    if(s[i] == '0') ++z_counter;
    else continue;
  }

  int ans = (lim - 1) - z_counter;
  cout << ans << "\n";

  return 0;
}