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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        char[] inputs = sc.next().toCharArray();
        int length = inputs.length;
        int[][] dp = new int[length][2];
        if (inputs[length - 1] == '0') {
            dp[length - 1][1] = 2;
        } else {
            dp[length - 1][0] = 1;
            dp[length - 1][1] = 1;
        }
        for (int i = length - 2; i >= 0; i--) {
            if (inputs[i] == '0') {
                dp[i][0] = Math.min(dp[i + 1][0], dp[i + 1][1] + 1);
                dp[i][1] = Math.min(dp[i + 1][0] + 2, dp[i + 1][1] + 1);
            } else {
                dp[i][0] = Math.min(dp[i + 1][0] + 1, dp[i + 1][1] + 2);
                dp[i][1] = Math.min(dp[i + 1][0] + 1, dp[i + 1][1]);
            }
        }
        System.out.println(Math.min(dp[0][0], dp[0][1] + 1));
    }
}

class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}