import java.util.Scanner;

public class crookedDigits {
    public static void main(String[] args) {
        Scanner user_input = new Scanner(System.in);


        String input = user_input.nextLine();

        long sum = 0;

        input = input.replace(".", "");
        input = input.replace("-", "");

        long number = Long.parseLong(input);

        while (number > 0) {
            sum = sum + number % 10;
            number = number / 10;
        }

        number = sum;
        long n = (long) number;

        while (n != 0) {
            if (sum > 9) {
                sum = 0;
                sum = sum + n % 10;
                n = n / 10;
                sum = n + sum;

            } else {
                System.out.println(sum);
                break;
            }
        }


    }
}