import java.util.Scanner;
public class Allsum {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		String S = s.nextLine();
		s.close();
		int sum = 0;
		for(int i = 0;i < S.length();i++){
			sum += Integer.parseInt(S.substring(i, i+1));
		}
		System.out.println(sum);

	}

}