Permissions – Can not run the comment sudo, even logged in as sudoers owner (the file / etc / sudoers belongs to the 1321 uid, but must be 0)

I've accidentally changed the owner for / etc ( sudo chown -R john / etc / when logged in as an administrator). I know it's wrong and that it affects / etc / sudoers as well. After that, I'm not able to launch the sudo of admin account and as well as John Account

Fault:

sudo: / etc / sudoers belongs to uid 1321, should be 0
sudo: no valid sudoers source found, abandon
sudo: unable to initialize the policy plugin

1321 is the uid of John. Get the same error when logged in as John. How to recover sudo to work

Trying to return to the property ( root chown -R / etc / ), error "Operation not allowed"

I use macOS Mojave