Refer to the given number series and answer the question that follows. Counting to be done from left to right only. All numbers are single-digit numbers only. (Left) 3 2 4 7 8 1 4 5 2 7 6 5 4 7 8 9 2 5 4 7 3 1 6 9 5 3 (Right) How many such odd digits are there, each of which is immediately preceded by an even digit and also immediately followed by an odd digit?