There are 3 bags A, B and C. Bag A contains 1 Red and 2 Green balls, bag B contains 2 Red and 1 Green balls and bag C contains only one Green ball. One ball is drawn from bag A and put into bag B then one ball is drawn from bag B and put into bag C and finally one ball is drawn from bag C and put into bag A. When this operation is completed, probability that bag A contains 2 Red and 1 Green balls, is -