Unable to install Ros Melodic on Ubuntu 18.04

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I am trying to install Ros Melodic on Ubuntu 18.04. I keep getting: E: Unable to locate package ros-melodic-desktop-full

When tracing the cause I found that when I run "sudo apt-get update" I always get:

E: Failed to fetch http://packages.ros.org/ros/ubuntu/di... 404 Not Found [IP: 64.50.233.100 80] E: Some index files failed to download. They have been ignored, or old ones used instead.

I tried everything found on the internet: sudo apt clean, deleting /var/lib/apt/lists/*, etc.

This is my /apt/etc/source.list:

# deb cdrom:[Ubuntu 18.10 _Cosmic Cuttlefish_ - Release amd64 (20181017.3)]/ cosmic main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us.archive.ubuntu.com/ubuntu/ cosmic main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ cosmic-updates main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ cosmic universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic universe
deb http://us.archive.ubuntu.com/ubuntu/ cosmic-updates universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ cosmic multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic multiverse
deb http://us.archive.ubuntu.com/ubuntu/ cosmic-updates multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ cosmic-backports main restricted universe multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ cosmic-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu cosmic partner
# deb-src http://archive.canonical.com/ubuntu cosmic partner

deb http://us.archive.ubuntu.com/ubuntu/ cosmic-security main restricted
# deb-src http://security.ubuntu.com/ubuntu cosmic-security main restricted
deb http://us.archive.ubuntu.com/ubuntu/ cosmic-security universe
# deb-src http://security.ubuntu.com/ubuntu cosmic-security universe
deb http://us.archive ...