How to get all unread news numbers of gnus?

Hi, everyone!

I want to write a function that notify gnus coming news.
And display unread news number in mode-line.

But I don't know how to get the numbers of all unread news after execute
command 'gnus-group-get-new-news'.

This have a command or variable that can do this?

Thanks for your help!

Regards.

Andy.