User blog comment:Nayuta Ito/Introduction to AAN/@comment-29014792-20160805233152/@comment-29014792-20160807112432

Now it's different.

Case B3: If there is the separator in the left and case B2 did not applied;
 * Copy the separator to R.
 * Replace the entry before the separator with '0 R 1'.
 * Continue the process within R separator.