class Program {

	private int factorial(int $num) {
		if($num == 0 || $num == 1)
			return 1;
		else
			return $num * $this->factorial($num - 1);
	}

	public void main() {
		int $num = 7;
		print('Factorial of ', $num, ' is ', $this->factorial($num), '.');
	}

}