import java.util.Scanner;

public class No289 {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        String num = s.next();
        int sum = 0;
        String[] c = num.split("");
        for (int i = 0; i < c.length; i++) {
            try {
                sum += Integer.parseInt(c[i]);
            } catch (NumberFormatException ignored) {
            }
        }
        System.out.println(sum);
    }
}