Putty: "ssh-rsa: command not found" error

I created key pair using puttygen.exe (local OS is windows 10). On Server (Ubuntu LTS). When I try connecting I’m getting ‘server refused our key’ and server asks for password.
After entering the password set for the user in my server,
I entered the command: cat .ssh/authorized_keys, I am entering the public key generated. Then I get an error “ssh-rsa: command not found”.

Their Might be a Wrong Command that you might have typed
What were you trying to accomplish?

usually their is no such command as ssh-rsa
You might have paste the ssh-rsa FDFD<Public-Key> on the Console By Mistake

Yes, you are right. Now my error is resolved.