import java.util.Scanner;
public class digitsum{
	public static void main(String[]args){
		Scanner kboard = new Scanner(System.in);
		char[]chars = kboard.nextLine().toCharArray();
		int total = 0;
		for(char c:chars){
			int x = Integer.parseInt(c+"");
			total+=x;
		}
		System.out.println(total);
	}
}