
\magnification=\magstep1
\parskip=4pt plus 6pt

\font\bigbf=cmbx10 scaled \magstep1
\font\bigit=cmti10 scaled \magstep1
\font\vbigbf=cmbx10 scaled \magstep2

\font\tenmsb=msbm10
\font\sevenmsb=msbm7
\font\fivemsb=msbm5
\newfam\msbfam
\textfont\msbfam=\tenmsb
\scriptfont\msbfam=\sevenmsb
\scriptscriptfont\msbfam=\fivemsb
\def\Bbb{\fam\msbfam}

\def\NN{{\Bbb N}}
\def\ZZ{{\Bbb Z}}
\def\QQ{{\Bbb Q}}
\def\RR{{\Bbb R}}
\def\CC{{\Bbb C}}
\def\TT{{\Bbb T}}
\def\SS{{\Bbb S}}
\def\bA{{\bf A}}
\def\bB{{\bf B}}

\def\nobf{\noindent\bf}
\def\nobigbf{\noindent\bigbf}
\def\sP{{\cal P}}

\def\emptyset{/\kern -0.67em{\scriptstyle\bigcirc}}

\def\floor#1{{\lfloor{#1}\rfloor}}

\def\vt{{\vrule height0.5pt width1pt depth0.5pt}}
\def\pvt{{\phantom{\vrule height0.5pt width1pt depth0.5pt}}}
\def\hedg{{\vrule height0.5pt width20pt depth0.5pt}}
\def\phe{{\phantom{\vrule height0.5pt width20pt depth0.5pt}}}
\def\vedg{{\vrule height10pt width1pt depth10pt}}

\def\vti#1{{\hbox to 1pt{\hidewidth%
\smash{\raise 2pt\hbox{${#1}$}}\hskip1pt\vrule height0.5pt width1pt depth0.5pt%
}}\ignorespaces}

\def\vtedg{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox{\vrule height10.6pt width0.2pt depth10.6pt}}%
\hss}}}
\def\htedg{{\hbox to 20pt{%
\hidewidth\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}}

\def\chup{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\uparrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10.6pt width0.2pt depth10.6pt\hidewidth}}%
\hss}}}
\def\chdown{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\downarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10.6pt width0.2pt depth10.6pt\hidewidth}}%
\hss}}}

\def\cxup{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\raise3pt\hbox{\lower\fontdimen22\textfont2\hbox{$\uparrow$}}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\uparrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower3pt\hbox{\lower\fontdimen22\textfont2\hbox{$\uparrow$}}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10.6pt width0.2pt depth10.6pt\hidewidth}}%
\hss}}}
\def\cxdown{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower3pt\hbox{\lower\fontdimen22\textfont2\hbox{$\downarrow$}}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\downarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\raise3pt\hbox{\lower\fontdimen22\textfont2\hbox{$\downarrow$}}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10.6pt width0.2pt depth10.6pt\hidewidth}}%
\hss}}}

\def\ctup{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\uparrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10pt width1pt depth10pt\hidewidth}}%
\hss}}}
\def\ctdown{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\downarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10pt width1pt depth10pt\hidewidth}}%
\hss}}}

\def\chright{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}%
\hss}}}
\def\chleft{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}%
\hss}}}

\def\cxright{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth\hglue6pt%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}\hglue6pt\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}%
\hss}}}
\def\cxleft{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}\hglue6pt\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth\hglue6pt%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}%
\hss}}}

\def\ctright{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.5pt width20pt depth0.5pt\hidewidth}}%
\hss}}}
\def\ctleft{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.5pt width20pt depth0.5pt\hidewidth}}%
\hss}}}

\def\hup{\smash{\hbox to 20pt{\hss%
\hbox to 0pt{\hidewidth%
\vrule height10.7pt depth10.7pt width0.4pt%
\hidewidth}%
\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\uparrow$}%
\hidewidth}%
\hss}}}

\def\hdown{\smash{\hbox to 20pt{\hss%
\hbox to 0pt{\hidewidth%
\vrule height10.7pt depth10.7pt width0.4pt%
\hidewidth}%
\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\downarrow$}%
\hidewidth}%
\hss}}}

\def\hright{\hbox to 1pt{\vrule height10pt depth10pt width0pt%
\hss\hbox to 0pt{\hidewidth%
\vrule height0.2pt depth0.2pt width21.4pt%
\hidewidth}%
\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\rightarrow$}%
\hidewidth}\hss}}

\def\hleft{\hbox to 1pt{\vrule height10pt depth10pt width0pt%
\hss\hbox to 0pt{\hidewidth%
\vrule height0.2pt depth0.2pt width21.4pt%
\hidewidth}%
\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$\leftarrow$}%
\hidewidth}\hss}}

