#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  string N;
  cin >> N;
  int len = N.size();
  vector<int> A;

  for (int i = len - 1; i >= 0; --i) {
    char ch = N[i];

    A.push_back(ch - '0');
  }

  A.push_back(0);
  vector<vector<int>> dp(len + 2, vector<int>(3, 9999999));
  dp[0][A[0]] = 0;

  for (int i = 0; i < len; ++i) {
    int v = A[i];
    int nv = A[i + 1];

    if (v == 1) {
      if (nv == 1) {
        dp[i + 1][1] = min(dp[i + 1][1], dp[i][1] + 1);
        dp[i + 1][2] = min(dp[i + 1][2], dp[i][2]);
        dp[i + 1][2] = min(dp[i + 1][2], dp[i][1] + 1);
      } else {
        dp[i + 1][0] = min(dp[i + 1][0], dp[i][1] + 1);
        dp[i + 1][1] = min(dp[i + 1][1], dp[i][2]);
        dp[i + 1][1] = min(dp[i + 1][1], dp[i][1] + 1);
      }
    } else {
      if (nv == 1) {
        dp[i + 1][1] = min(dp[i + 1][1], dp[i][0]);
        dp[i + 1][2] = min(dp[i + 1][2], dp[i][1] + 1);
        dp[i + 1][2] = min(dp[i + 1][2], dp[i][2] + 1);
      } else {
        dp[i + 1][0] = dp[i][0];
        dp[i + 1][0] = min(dp[i + 1][0], dp[i][1] + 1);
        dp[i + 1][1] = min(dp[i + 1][1], dp[i][2] + 1);
      }
    }

    // fprintf(stderr, "(%d, %d, %d)\n", dp[i + 1][0], dp[i + 1][1], dp[i + 1][2]);
  }

  cout << min(dp[len][0], dp[len][1] + 1) << endl;

  return 0;
}