Bootstrap 4. How to write order?

Question

Bootstrap

Tell the teapot. On three I did this:

<div class='col-xs-12 col-sm-12 col-md-7 col-md-push-2'>Основное содержание</div>
<div class='col-xs-12 col-sm-12 col-md-3 col-md-pull-7 col-md-push-2'>Правый блок</div>
<div class='col-xs-12 col-sm-12 col-md-2 col-md-pull-10'>Левый блок</div>

But I have no idea how to do it on 4.

On large screens, the main content is in the center, the left block is on the left, the right is on the right.
And the fact that less md sm xs is needed like this:
Main content on top, then on the bottom right block, and then on the bottom left block

Answer 1

for example like this: