Mavericks downloaded but not installed

after a long effort i ve downloaded the Mavericks and the mac asked me , " your update is downloaded and ready to be installed" i clicked restart and install.

Mac is restarted but after booting up, it hasnt installed the Mavericks. When i go to the app store it again shows, " download" option .

As its already downloaded to my mac, how do i install it locally ? where is the location of the file?

Thanks,