(1) Write a Dafny program that:

  takes a sequence of integers and returns the unique elements of that list. There is no requirement 
  on the ordering of the returned values.

Information about sequences can be found at: https://rise4fun.com/Dafny/tutorialcontent/Sequences

Provide appropriate pre- and post-conditions, and loop invariants to verify the correctness of 
your solution.  You must provide justification for your specification in the comments that describe
the solution.  

(2) Write a Dafny program that:

  takes a padding character, a string, and a total length, returns the string padded to that length 
  with that character. If length is less than the length of the string, does nothing.

As before, you need to both justify (via comments) and verify (via suitably define pre/post conditions 
and loop invariants) the correctness of your implementation.