import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        char[] arr = br.readLine().toCharArray();
        boolean isUp = false;
        int count = 0;
        for (int i = arr.length - 1; i >= 0; i--) {
            boolean now = arr[i] == '1';
            if (isUp ^ now) {
                count++;
                if (i != 0 && arr[i - 1] == '1') {
                    isUp = true;
                } else {
                    isUp = false;
                }
            }
        }
        if (isUp) {
            count++;
        }
        System.out.println(count);
   }
}