#include <bits/stdc++.h>
const double PI = acos(-1), EPS = 1e-7;
const int OO = 0x3f3f3f3f, N = 1e7 + 5, MOD = 1e9 + 7;
using namespace std;
void fast() {
  std::ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
}
vector<unsigned long long> v(101000);
void fib() {
  v[0] = 0;
  v[1] = 1;
  for (int i = 2; i < 101000; i++) v[i] = (v[i - 1] + v[i - 2]) % MOD;
}
string sum(string s) { return s; }
int main() {
  fast();
  string s;
  cin >> s;
  long long z = s.length() - 1;
  long long ans = 0;
  while (z >= 1) {
    if (s[z] == '0') {
      s.erase(s.begin() + z);
      z--;
    } else {
      char carry = '1';
      for (int i = s.length() - 1; i >= 0; i--) {
        if (carry == '1' && s[i] == '1') {
          s[i] = '0';
          carry = '1';
        } else if (carry == '1' && s[i] == '0') {
          carry = '0';
          s[i] = '1';
          break;
        }
      }
      if (carry == '1') {
        s = '1' + s;
        z++;
      }
    }
    ans++;
  }
  cout << ans << "\n";
  return 0;
}
