O’Brien writes something on a piece of paper and gives it to Winston. He writes what he writes just in front of a telescreen. What does he write on the paper?

In Book Two, chapter six, Winston is casually walking down a corridor at the Ministry of Truth when he runs into O'Brien. O'Brien stops Winston and proceeds to compliment him on a particular article that he had written in the Times. O'Brien then mentions that he shares the same opinion of Winston's writing as one of his former friends, whose name he cannot seem to remember. Winston immediately recognizes that O'Brien is referring to Syme, who is now an unperson. O'Brien's allusion to Syme indicates that he is also a political dissident and can be trusted. O'Brien goes on to mention that he noticed Winston used two words in his article which are now obsolete. In full view of the telescreen, O'Brien writes his address on a scrap sheet of paper and tells Winston to visit his apartment in order to pick up the new tenth edition of the Newspeak dictionary.