#include <bits/stdc++.h>
using namespace std;
int res;
int tox[] = {0, 0, 1, -1};
int toy[] = {1, -1, 0, 0};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr), cout.tie(nullptr);
  string s;
  cin >> s;
  while (s.back() == '0') s.erase(s.size() - 1, 1), res++;
  while (s != "1") {
    while (s.size() && s.back() == '1') s.erase(s.size() - 1, 1), res++;
    res++;
    if (!s.size()) break;
    s.back() = '1';
  }
  cout << res;
  return 0;
}
