Dear Yelena Sergeyevna

Three school boys and one school girl visited their old schoolmarm on her birthday. But their intentions were horrible. Four school graduates congratulate their teacher of mathematics Yelena Sergeyevna on her birthday and ask her to return them their graduate works on mathematics in order to change them before the marks. Yelena Sergeyevna strongly objects... —Svetlana Rubinshtein <svetlachok@hotmail.com>