How to get admin rights after failed editing sudoers in Ubuntu?

Question

ubuntu

Inadvertently changed the file /etc/sudoers. Now I can no longer get admin rights in the system. Error:
:~$ sudo vim /etc/sudoers
>>> /etc/sudoers: syntax error near line 31 <<<
sudo: parse error in /etc/sudoers near line 31
sudo: no valid sudoers sources found, quitting
sudo : unable to initialize policy plugin.
I tried to get rights through pkexec visudo, but also an error occurs after entering the user password:
polkit-agent-helper-1 error response to policykit daemon
Has anyone encountered this problem and what should I do?

Answer 1

A very bad, but in theory working option is to log in as root and edit sudoers from under it (without the sudo command)