import java.util.*;
import java.io.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		PrintWriter ou = new PrintWriter(System.out);
		char[] s = sc.next().toCharArray();
		int n = s.length - 1;
		for(char i : s) if(i == '0') n--;
		ou.println(n);
		ou.flush();
		sc.close();
	}
}