#include <bits/stdc++.h>
using namespace std;
int a[1000009];
long long dec_bin(string s) {
  long long res = 0;
  for (int i = 0; i < s.size(); i++) {
    res += pow(2, i) * (s[s.size() - 1 - i] - '0');
  }
  return res;
}
int main() {
  string s;
  long long c = 0;
  cin >> s;
  int idx = 0;
  reverse(s.begin(), s.end());
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '0') a[idx++] = i;
  }
  if (idx == 0) {
    if (s.size() == 1)
      cout << 0;
    else
      cout << s.size() + 1;
    return 0;
  }
  if (idx == s.size() - 1) {
    cout << idx;
    return 0;
  }
  int i = 1;
  if (a[0] != 0)
    c += a[0] + 1;
  else
    while (a[i] - a[i - 1] == 1) c++, i++;
  for (i; i < idx; i++) {
    c += (a[i] - a[i - 1]) + 1;
  }
  if (a[idx - 1] < s.size()) c += (s.size() - a[idx - 1]) + 1;
  cout << c;
  return 0;
}
