import java.util.Scanner;

public class crookeddigits {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String n = scanner.nextLine().toString().replaceAll("\\.", "").replaceAll("-","");
        int a = 0;
        for (int i = 0; i < n.length(); i++) {
            a += Character.digit(n.charAt(i), 10);
        }


    String b ="";

        if (a > 9) {
            while(true) {
                if (a <= 9) {
                    System.out.println(a);
                    break;
                } else {
                    b = a+"";
                    a = 0;
                    for (int i = 0; i < b.length(); i++) {
                        a += Character.digit(b.charAt(i), 10);
                    }
                }
            }
        } else {
            System.out.println(a);
        }


    }
}