import java.util.Scanner;
import java.util.Arrays;
import java.util.List;
public class No289 {

	public static void main(String[] args) {
		
		int count=0;
		
		Scanner in = new Scanner(System.in);
        String str = in.next();
        List<String> list = Arrays.asList(str.split(""));
        for(String q :list){
        	count += toInt(q);
        }
		in.close();
        System.out.println(count); 
	}
	
	public static int toInt(String str){
		int ans = 0;
		
		try{
			ans = Integer.parseInt(str);
		}
		catch(Exception ex){
			
		}
		return ans;
	}

}