/**
     * Problem 20
     *
     * n! means n × (n − 1) × ... × 3 × 2 × 1
     * Find the sum of the digits in the number 100!
     */
    public void Problem120() throws Exception {

        BigInteger n = BigInteger.ONE;
        
        for (int i = 1; 100 >= i; i++) {
            n = n.multiply(BigInteger.valueOf(i));
        }

        System.out.println(100 + "! = " + n);

        int sum = 0;
        String[] numbers = n.toString().split("");

        for (int i = 1; i < numbers.length; i++) {
            sum += Integer.valueOf(numbers[i]).intValue();
        }

        System.out.println(sum);
    }