windows 8.1 update for lumia 520

[WPCentral Question]

i updated my lumia 520 to 8.1 using preview for developers app and now when the official 8.1 update came i tried downloading and it stopped midway and now im trying to search fr that update again by going to seetings and it is showing that 'we are unable' to find updates. Can anyone tell me that how can i get that update again