import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String S = sc.next();
        int sum = 0;
        for (int i = 0; i < S.length(); i++) {
            sum += Integer.parseInt(S.substring(i, i + 1));
        }
        System.out.println(sum);
    }
}