How to make up the admin panel menu?

Question

css

Hello, you need to make the layout of the admin panel, the frame itself, depicted schematically below.
On the left there is a menu, 200 pixels wide, in the center is the content part, 1000 pixels wide.
How best to wrap it up, what would be without crutches.
My option is to place the menu + in the center of the content part, find the width at which the menu will climb onto the content part and simply press it to the right side of the screen.
Perhaps there is a more practical and correct option?