import java.util.Scanner;
import java.lang.Integer;

public class Main {
    public static void main(String[] args) {
    		Scanner sc = new Scanner(System.in);
    		String s = sc.next();
    		int number = 0;
    		if(!s.matches(".*[0-9].*")){
    			System.out.println(number);
    		}else{
    		String intStr= s.replaceAll("[^0-9]","");
    		int num = Integer.parseInt(intStr);
    		System.out.println(sumDigits(num));
    		}
    }
    
    public static int sumDigits(int n) {
        int sum = 0;
        while (n != 0) {
            sum += n % 10;
            n /= 10;
        }
        return sum;
    }
}