import java.util.Arrays;
import java.util.HashMap;
import java.util.Scanner;

public class Main {
    static long[] a=new long[1000005];
    static long[] b=new long[1000005];
    static int[] c=new int[200005];
    static int[] d=new int[500005];
    static int[] e=new int[200005];
    static int[] f=new int[200005];
    static int t=520;
    static int ans=0;
    static int max=-1;
    static int min=(int)2e+9;
    static int n=0;
    static int m=0;
    static int sum=0;
    static int l=0;
    static int r=0;

    static HashMap<Integer,Integer> map=new HashMap<>();
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String s=sc.nextLine();
        if(s.charAt(0)=='1'&&s.length()==1){
            System.out.println(ans);
            System.exit(0);
        }
        StringBuilder s1=new StringBuilder();
        t=s.length()-1;
        while(t>=0&&s.charAt(t)!='1') {
            t--;
        }
        l=t;
        ans=s.length()-t-1;
        if(t==0){
            System.out.println(ans);
            System.exit(0);
        }
        s1.append(s.substring(0,t+1));
        while(true) {
            if(s1.length()==1) {
                break;
            }
            r=s1.length()-1;
            while(s1.charAt(l)!='0') {
                if(l==0){
                    break;
                }
                l--;
            }
            ans+=(1+(r-l));
            if(l==0){
                break;
            }

            s1.delete(l,r+1);
            s1.append('1');
            if(s1.length()==1) {
                break;
            }
        }
        System.out.println(ans+1);
    }
}