;; read in a non-negative integer n and write (n-1)! + (n-2)!

    allocate-registers n, cont, factorial, fact, zero, one, test, loop, first, second, result

    li factorial factorialL
    li zero 0
    li one 1
    li first firstL
    li second secondL
    li loop loopL

    read n

    sub n n one
    li cont firstL
    j factorial
firstL::
    add result fact zero
    sub n n one
    li cont secondL
    j factorial
secondL:
    add result result fact 
    write result
    halt

    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    ;; compute n! iteratively
    ;; n - input
    ;; fact - output
    ;; cont - return address
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
factorialL:
    li fact 1
loopL:
    sgt test n zero
    jeqz test cont
    mul fact fact n
    sub n n one
    j loop