Well, I've got a little problem with my SSD.
I had Windows installed through the bootcamp, when macOS offered me a High Sierra update. I've updated. But when I wanted to remove Windows, I could not do it. I had to delete it via the Disk Utility. And then I ran into a problem: I had 2 containers on one internal physical disk.
But how do I unite them now, so that the empty merged with the system without loss of information?
Here is my diskutil list: