Appendix 3. Chronicles of Torus
Bezhaev A.Yu.
The site sql-ex.ru presents several tasks, connected with the mythical planet by the name Torus. This paragraph gives a brief introduction to planet topology and explains terminology.
In mathematical sense, torus is a surface of revolution generated by revolving a circle in three-dimensional space (see http://en.wikipedia.org/wiki/Torus). It has a bagel (boublik) form.