Перельман умный... польститесь? )) http://ru.wikipedia.org/wiki/%CF%E5%F0%E5%EB%FC%EC%E0%ED,_%C3%F0%E8%E3%EE%F0%E8%E9_%DF%EA%EE%E2%EB%E5%E2%E8%F7#.D0.98.D0.BD.D1.82.D0.B5.D1.80.D0.B5.D1.81.D0.BD.D1.8B.D0.B5_.D1.84.D0.B0.D0.BA.D1.82.D1.8B