How to do it?

 From:  AlexS (ALEKSEI)
BurrMan, Michael Gibson: thank you so much!

I understand that the program itself can not figure out what to do in a given case. But if such curves a lot, what do you do? Each curve will have to edit?

As I recall, in Google Sketchup no such problem, although there is another principle of modeling - the polygon.

In any case, thanks again for your help!