\def\S{\mbox{\large $\rhd\!\!\!\lhd$}} \def\Aa{\vec{\cal A}{\it ct}} \def\cA{{\cal A}} \def\cS{{\cal S}} \def\cC{{\cal C}} \def\cE{{\cal E}} \def\cR{{\cal R}} \def\Ac{{\cal A}{\it ct}} \def\bms{\{\!|\,} \def\ems{\,|\!\}} \def\lra{\longrightarrow} \def\lera{\leftrightarrow} \def\vlra{-\hspace{-0.2cm}-\hspace{-0.2cm}\lra} \def\notsim{\sim \hspace{-3.5mm} /\;} \def\notequiv{\equiv \hspace{-3.5mm} /\;} \def\noapprox{\approx \hspace{-3.5mm} /\;} \def\rmdef{\stackrel{\mbox{\em {\tiny def}}}{=}} \def\eq{\mbox{\boldmath $=$}} \def\Chi{\mbox{\Large $\chi$}} \def\E{\cC/{\cong}} \def\Eup{\cC/({\cong} \cR^{*} {\cong})} \def\mscup{\uplus} \def\mscap{\cap} \def\fcomp{\raisebox{0.6ex}{\mbox{\tiny $\circ$}\,}} \newfont{\cmexx}{cmex7} \newcommand{\smallrhd}{\mathrel{\raise23pt\hbox{\cmexx\symbol{}}}} \newcommand{\smalllhd}{\mathrel{\raise23pt\hbox{\cmexx\symbol{}}}} \def\smallS{\mbox{\tiny $\rhd \!\!\!\lhd$}} \newcommand{\ssync}[1]{\raisebox{-0.9ex}{$\: \stackrel{\smallS}{\scriptscriptstyle #1}\,$}} \renewcommand{\infty}{\top} \mathchardef\infinity="0231 \def\QED {{\unskip\nobreak\hfil\penalty50 \hskip2em\hbox{}\nobreak\hfil$\Box$ \parfillskip=0pt \finalhyphendemerits=0 \par}} \def\separate{\begin{center} ---\hspace{-0.12mm}---\hspace{-0.12mm}--- \hspace{-1.5mm}$\circ$\hspace{-1.5mm} ---\hspace{-0.12mm}---\hspace{-0.12mm}--- \end{center}} \newcommand{\mult}[2]{m_{#1}(#2)} \newcommand{\sync}[1]{\raisebox{-1.0ex}{$\;\stackrel{\S}{\scriptscriptstyle #1}\,$}} \newcommand{\seq}[1]{\stackrel{\rhd}{\scriptscriptstyle #1}} \newcommand{\equ}[1]{\stackrel{#1}{\eq}} \newcommand{\mat}[1]{\mbox{\bf #1}} \newcommand{\NIL}{\mbox{{\bf 0}}} \endinput