allocate-registers n, cont, downUp, baseCase, sp, one
li one, 1
li downUp, LdownUp
li baseCase, LbaseCase
li sp, 0

read n
li cont, LafterTopLevel
j downUp

LafterTopLevel:
halt

;; that's the end of the main program
;; now we can write downUp

LdownUp:
jeqz n, baseCase

write n
; call downUp(n-1)
st n, sp
add sp, sp, one
st cont, sp
add sp, sp, one
sub n, n, one
li cont, LafterTheRecursiveCall
j downUp

LafterTheRecursiveCall:
sub sp, sp, one
ld cont, sp
sub sp, sp, one
ld n, sp
write n
j cont

LbaseCase:
write n
j cont