import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        long sum = 0;
        String x = scan.next();
		for(int i = 0 ; i < x.length() ; i++){
			sum += Character.getNumericValue(x.charAt(i));
		}
		System.out.print(sum);
    }
}