Client not updating

When I opened League, it said that the update is required. I pressed restart client button. Update has begun and after 30 seconds I got this: ,,There was a problem patching League of Legends. We'll restore a backup version and try updating again after you restart the patcher." I restarted the client : ,,We have restored this installation to an older version of League of Legends. now we'll try to patch it up to the latest version" Then I try to patch it again and get the same results.. How can i fix it?