#include <bits/stdc++.h>
using namespace std;

int main() {
  string N;
  cin >> N;

  reverse(N.begin(), N.end());
  N.push_back('0');

  vector<vector<int>> dp(N.size() + 1, vector<int>(2, N.size()));
  dp[0][0] = 0;
  for (int i = 0; i < N.size(); ++i) {
    for (int j = 0; j < 2; ++j) {
      int s = j + N[i] - '0';
      if (s < 2) dp[i + 1][0] = min(dp[i + 1][0], dp[i][j] + (s != 0));
      if (0 < s) dp[i + 1][1] = min(dp[i + 1][1], dp[i][j] + (s != 2));
    }
  }

  cout << dp[N.size()][0] << endl;

  return 0;
}