#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  string s;
  cin >> s;
  reverse(s.begin(), s.end());
  vector<int> dp(2, 1 << 30);
  dp[0] = 0;
  for (char c : s) {
    vector<int> nxt(2);
    int x = c - '0';
    if (x == 0) {
      nxt[0] = min(dp[0], dp[1] + 1);
      nxt[1] = dp[1] + 1;
    }
    if (x == 1) {
      nxt[0] = dp[0] + 1;
      nxt[1] = min(dp[0] + 1, dp[1]);
    }
    swap(dp, nxt);
  }
  cout << min(dp[0], dp[1] + 1) << '\n';
  return 0;
}