import java.util.Scanner;
 
/**
 *
 * @author islam
 */
public class Hh {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
Scanner in =new Scanner(System.in);
 
 
String x=in.next();
int y=Integer.valueOf(x);
int sum=0;
for (int i=0 ; i<x.length();i++){
int z=y%10;
sum+=z;
y=y/10;
 
}
 
        System.out.println(sum);
    }
 
}