:: open a gate that takes an unsigned decimal and give it a face, n
::
|=  n=@ud
:: let t be an unsigned decimal with an initial value of 1
::
=/  t=@ud  1
:: return to this point of recursion if the following condition is not met
::
|-
:: if n is 1, return t.  Otherwise, continue to the next line
::
?:  =(n 1)
    t
:: decrease n by 1, multiply t by n, and return the new values of n and t to the point of recursion
::
$(n (dec n), t (mul t n))