Multiple blogs: how to hide the sidebar for one blog only

Site URL: https://dachshund-dory-ba76.squarespace.com

I'm building a site which uses three different blogs for various purposes. We use the sidebar in two of those but not on the third. What custom CSS can I use to hide the sidebar on the individual posts for a single blog.

An example post is here: https://dachshund-dory-ba76.squarespace.com/offerings-details/leading-purposeful-conversations

Password for the website is 'kyoto2019'

Thanks @tuanphan. That works nicely. Note to self (and others who may run into this issue): the code injection needs to be made to the blog settings (on the blog page), not to a summary page. To explain, for this blog we display a page with a summary block rather than the blog page itself. Originally I added the code to the former, where (of course) it made no difference.

@tuanphan, I'm now creating a second blog on my site too using the Avenue template, but tried to put this code into the Blog Settings > Advanced > Page Header Code Injection as you specified, but still seeing the sidebar on this new blog.  Any suggestions? 

13 hours ago, geoffwilsonhcd said:

@tuanphan, I'm now creating a second blog on my site too using the Avenue template, but tried to put this code into the Blog Settings > Advanced > Page Header Code Injection as you specified, but still seeing the sidebar on this new blog.  Any suggestions? 

Hi. Can you share link to a blog? We can help easier