I recently heard about UbuntuShowdown apps. There are some very nice apps which I really want to try. I am trying to install these apps by adding repositories as it is mentioned on their page. But at the completion of command, it is showing:

```
unable to locate package <package name>

```

For example, after running this command in terminal:

```
sudo add-apt-repository ppa:brianrobles204/xkcd-browser
sudo apt-get update
sudo apt-get install xkcd-browser

```

I am getting this at the end

```
unable to locate package xkcd-browser

```

Please help.

[UbuntuShowDown Apps](https://wiki.ubuntu.com/AppDevelopers/AppShowdown/CommunityVote#Applications)