// editor1
import java.util.*;
public class sumdidi {
    public static void main (String [] args) {
        Scanner sc =new Scanner(System.in);
        int num = sc.nextInt();
        int sum = 0;
        while( num != 0) {
            int digi = num%10;
            sum = sum+digi;
            num = num/10;
            return sum;
        }
        //System.out.println(sum);
    }
}