Appendices numbering by cyrillic letters, problem with \Asbuk [closed]

Question

I hope that someone can help me with this.

I am trying to number my appendices in a book by cyrillic letters (А,Б,В,Г,Д instead of A,B,C,D,E). I have found that \Asbuk produces capital cyrilic letters instead of latin ones. I first define \Asbuk by

\def\Asbuk#1{\expandafter\russian@Alph\csname c@#1\endcsname}
 \if@uni@ode
 \def\russian@Alph#1{\ifcase#1\or
 А\or Б\or В\or Г\or Д\or Е\or Ж\or
 З\or И\or К\or Л\or М\or Н\or О\or
 П\or Р\or С\or Т\or У\or Ф\or Х\or
 Ц\or Ч\or Ш\or Щ\or Э\or Ю\or Я\else\@ctrerr\fi}
 \else
 \def\russian@Alph#1{\ifcase#1\or
 \CYRA\or\CYRB\or\CYRV\or\CYRG\or\CYRD\or\CYRE\or\CYRZH\or
 \CYRZ\or\CYRI\or\CYRK\or\CYRL\or\CYRM\or\CYRN\or\CYRO\or
 \CYRP\or\CYRR\or\CYRS\or\CYRT\or\CYRU\or\CYRF\or\CYRH\or
 \CYRC\or\CYRCH\or\CYRSH\or\CYRSHCH\or\CYREREV\or\CYRYU\or
 \CYRYA\else\@ctrerr\fi}
 \fi

and later try to number the appendices by

\renewcommand{\thechapter}{\Asbuk{chapter}}

However, it does not work.

Similar problem appears when I try to change the latin alphabetical order in Index to cyrilic alphabet...

I would appreciate any help. Thanks in advance!