digits

import java.math.BigInteger;
import java.util.Scanner;

public class CrockedNumberVar2Dgudj {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();
        String textNumber = input.replace("-", ""); // Remove the negative sign if present

        BigInteger currentNumberSum = BigInteger.ZERO;
        BigInteger bigIntegerSumDigits2 = BigInteger.ZERO;

        for (int i = 0; i < textNumber.length(); i++) {
            BigInteger tempDigit = BigInteger.valueOf(Character.getNumericValue(textNumber.charAt(i)));
            currentNumberSum = currentNumberSum.add(tempDigit);
        }

        BigInteger sumDigits = currentNumberSum.add(BigInteger.valueOf(Character.getNumericValue(textNumber.charAt(textNumber.length() - 1))));

        String textNumberSumDigits = sumDigits.toString();

        for (int i = 0; i < textNumberSumDigits.length(); i++) {
            BigInteger tempDigit2 = BigInteger.valueOf(Character.getNumericValue(textNumberSumDigits.charAt(i)));
            bigIntegerSumDigits2 = bigIntegerSumDigits2.add(tempDigit2);
        }

        System.out.println(bigIntegerSumDigits2);
    }
}