When importing a .csv file what is the backlog and unassigned user jira id to import?

[Michael Born]

I am trying to import from Rational to JIRA.  During the import process I do not want to put my items in a Sprint.  I want them in the backlog.  I tried leaving it blank, null, 0 values but it still fails the validation.  Is there a unique ID value for the backlog that I can place in the import box.

Also,
What would a unassigned user id be?

Food for thought.  Thanks ahead of time for any comments.