public static void main(String[] args) {

        System.out.println(sumDigits(125));

    }

    public static int  sumDigits (int number) {
        if (number <= 9) {
            return -1;
        } else {
            int lastNumber = 0;
            int sum = 0;
            while (number > 9) {
                lastNumber = number % 10;
                number = number / 10;
                sum += lastNumber;
            } return sum;
        }
    }
}