;; file: gcd.s
;; author: SS
;; date: Sep 9, 2019
;;
;; This program reads in two nonnegative integers a and b,
;; then prints their gcd.
;;
;; The SLIM code translates the following python code:
;;
;; a = int(input())
;; b = int(input())
;; while b > 0:
;;     a, b = b, a%b
;; print(a)

    allocate-registers zero a b loop write r test

    li zero 0

    li loop loopL
    li write writeL

    read a
    read b

loopL:
    sgt test b zero
    jeqz test write
    rem r a b
    sub a a a
    add a a b
    sub b b b
    add b b r
    j loop

writeL:
    write a
    halt