2. n! = n × (n-1) × (n-2) × ... × 2 × 1
	  ^
          ^
      Compute this product FIRST
      and call result A

      =         A × (n-2) × ... × 2 × 1
		  ^
		  ^
             Compute this product NEXT
             and call result A

      =                 A × ... × 2 × 1
                     .
                     . (etc.)
                     .
      =                           A × 1