This question already has an answer here:
If I am not able to right click on CMD and run as administrator, or CTRL + Shift + Enter to run CMD, but I am using an administrative user account in a non-admin shell (CMD.exe); How in the world do I escalate to an admin from that shell?
Runas does not seem to have a switch for escalation. Assume I do not know the password for the user called Administrator. I am just a normal user in the Administrators group.
Preferably without using some 3rd party app, but I will take what I can get.