git rebase of three already merged branches into one?

Question

I have these three branches that looks something like this:

A1--A2----A3--...--An----AB1--AB2--..--ABn--ABC
     \  \                /                  /
      \  C1-------------+------------------/ 
      B1--B2--...--Bn--/ (B merges to A)

I want to rebase them into single branch. How would you advise me to do it? The order of commits if those of C precede the As or or Bs - Cs does not much matter.