import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        final Scanner scanner = new Scanner(System.in);
        final String in = scanner.nextLine();
        int result = 0;
        for (int i = 0; i < in.length(); i++) {
            int index = in.charAt(i);
            if (index > 57) continue;
            if (index < 48) continue;
            result++;
        }
        System.out.println(result);
    }
}