How to automatically install updates in linux mint 17.1

I have linux mint 17.1 xfce, and I am wondering how to automatically install updates. Every time a new update is available I have to click on the mintUpdate icon on the panel and enter my password and click install. I think it is supposed to be good to install manually so that you can judge whether or not you really want to install the update. But I have never in two years decided that I didn't want to install an update, so I think it would be easier to just have it done automatically in the background.

Now I found a webpage purporting to explain how to install updates automatically. But I don't think it does a good job of explaining which updates will get installed automatically if you follow their instructions. It gives a configuration file to use that looks like this

// Automatically upgrade packages from these (origin, archive) pairs 

Unattended-Upgrade::Allowed-Origins { 

"${distro_id} ${distro_codename}-security"; 

// "${distro_id} ${distro_codename}-updates"; 

// "${distro_id} ${distro_codename}-proposed"; 

// "${distro_id} ${distro_codename}-backports"; 

}; 

but it doesn't explain how these origins map onto mintUpdate's "levels".

My goal is to install all updates classified as level 1, 2, or 3 by mintUpdate as well as all security updates. But I don't want to install non-security updates for level 4 or 5. How would I do this?