Write a recursive procedure called reverse that takes a binary tree BinTree as input and returns its reverse as the output.

A binary tree is reversed if its left subtree is replaced with its right subtree and vice versa.

Below are a few examples of inputs/outputs of the reverse procedure.

> (reverse 7)

7

> (reverse '(+ 7 8))

'(+ 8 7)

> (reverse '(* (+ 7 8) (- 10 11) ) )

'(* (- 11 10) (+ 8 7) )

BinTree is defined by the following grammar. In this grammar, Int denotes an integer number and Symbol denotes +,-,/ and *.

Bintree ::= Int | (Symbol Bintree Bintree)