;; def sumDigits(n):
;;    if n == 0:
;;        return 0
;;    else:
;;        return sumDigits(n // 10) + n % 10

    allocate-registers cont ans x ten sp one sumDigits n baseCase

    li sp 0
    li one 1
    li ten 10
    li sumDigits LsumDigits
    li baseCase LbaseCase

    li cont LafterSumDigits
    read n
    j sumDigits

LafterSumDigits:
    write ans
    halt

;; sumDigits - computes sum of digits
;; registers used:
;;     input -- n
;;     output -- ans
;;     continuation -- cont
;;
LsumDigits:
    jeqz n baseCase

    st cont sp
    add sp sp one
    st n sp
    add sp sp one

    quo n n ten
    li cont LafterRecursiveCall
    j sumDigits
    
LafterRecursiveCall:
    sub sp sp one
    ld n sp
    sub sp sp one
    ld cont sp

    rem x n ten
    add ans ans x
    j cont
     
LbaseCase:
    li ans 0
    j cont