#include <bits/stdc++.h>
using namespace std;
long long t = 1;
void solve() {
  vector<char> v;
  long long ans = 0;
  string s;
  cin >> s;
  for (long long i = 0; i < s.length(); i += 1) {
    v.push_back(s[i]);
  }
  if (s.length() == 1) {
    cout << "0";
    return;
  }
  long long nahi = 0;
  for (long long i = 1; i < s.length(); i += 1) {
    if (s[i] == '1') {
      nahi = 1;
    }
  }
  if (nahi == 0) {
    cout << s.length() - 1;
    return;
  }
  long long flag = 0;
  do {
    if (v[v.size() - 1] == '1') {
      flag = 0;
      for (long long i = v.size() - 1; i >= 0; i--) {
        if (v[i] == '1')
          v[i] = '0';
        else {
          flag = 1;
          v[i] = '1';
          ans++;
          break;
        }
      }
      if (flag == 0) {
        v.insert(v.begin(), '1');
      }
    }
    ans++;
    v.pop_back();
  } while (v.size() != 1);
  cout << ans + 1;
}
int main() {
  int i;
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  while (t--) solve();
  return 0;
}
