#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(NULL);
  cin.tie(NULL);
  string s;
  cin >> s;
  long long int n, i, j, cnt;
  n = s.length();
  cnt = j = 0;
  for (i = 0; i < n; i++) {
    if (s[i] == '1') {
      cnt++;
      j = i;
    }
  }
  if (cnt == 1)
    cout << n + j - cnt;
  else
    cout << n + j - cnt + 2;
  return 0;
}
