'''
problem4.py (25 points)
===

Author:  



Write a program that:

* asks the user for their three favorite vegetables
* uses the print() function three times (only three times) to 
    * print out every vegetable separated by commas, in the order entered
    * print out every vegetable again, in reverse order, each on a separate line
    * print out every vegetable again, in reverse order, each on a separate line
    with an exclamation point at the end

Use the print() function with the `sep` keyword to do this. 


Example Interaction
=====
Please enter your first favorite vegetable
> zucchini  
Please enter your second favorite vegetable
> cauliflower
Please enter your third favorite vegetable
> chocolate ice cream


zuccchini, cauliflower, chocolate ice cream

chocolate ice cream
cauliflower
zucchini

chocolate ice cream!
cauliflower!
zucchini!

 
'''