Need help with PROLOG.

write a PROLOG predicate my_sort(Unsorted, Sorted) using the following pseudocode outline: Base cases go first. my_sort(Unsorted, Sorted) :- Max is the largest element of Unsorted and Unsorted2 is what is left after removing Max from Unsorted and the sorted version of Unsorted2 is Sorted2 and Sorted2 is Sorted without its last element Max. Note: Use the builtin append and select predicates. 

Test on: sorting [2, 1, 1, 3, 2]