import java. util. Scanner;

public class Main{
	public static void main (String[] args){
		Scanner scanner = new Scanner (System. in);
		
		String number = scanner. next();
		
		int x = 0;
		String[] count = number. split ("");
		
		for (int j = 0; j < number. length(); j ++){
			Integer a = Integer. parseInt (count[j]);
			x += a;
		}
		System. out. println (x);
	}
}