import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		s = s.replaceAll("[A-Za-z]", "");
		if(s.length() == 0) {
			System.out.println(0);
		} else {
			int ans = 0;
			for(int i = 0 ; i < s.length() ; i++) {
				ans += s.charAt(i) - '0';
			}
			System.out.println(ans);
		}
	}
}