def last_name_first(n):
    """
    Returns: copy of n but in the form 'last-name, first-name'

    We assume that n is just two names (first and last).  Middle
    names are not supported.

    Examples:
        last_name_first('Walker White') returns 'White, Walker'
        last_name_first('Walker      White') returns 'White, Walker'

    Parameter n: the person's name
    Precondition: n is in the form 'first-name last-name' with one
    or more spaces between the two names. There are no spaces in
    either <first-name> or <last-name>
    """

    print('Starting last_name_first with "'+n+'"')

    end_first = n.find(' ')
    print('end_first is "'+str(end_first)+'"')

    first = n[:end_first]
    print('first is "'+str(first)+'"')

    last  = n[end_first+1:]
    print('last is "'+str(last)+'"')

    print('Finishing last_name_first')

    print() # prints a blank line
    return last+', '+first