input fks
verbatimtex
%&latex
\documentclass[9pt]{extarticle}
\usepackage[utf8]{inputenc}
\usepackage{fkssugar}
\begin{document}
etex
 
prologues:=3;
 
beginfig(1);
u:=0.6cm;
draw origin--(5u,0)--(5u,4u)--(0,4u)--cycle;
draw fullcircle scaled (u/2) shifted (u,-u/4);
draw fullcircle scaled (u/2) shifted (4u,-u/4);
draw (-u,-u/2)--(7u,-u/2);
draw (u,4u)--(2u,4u)--(2u,5u)--(u,5u)--cycle;
draw ((u,4u)--(2u,4u)--(2u,5u)--(u,5u)--cycle) shifted (4u,-3u);
draw fullcircle scaled (u/2) shifted (5.3u,4.3u);
draw (2u,4.55u)--(5.3u,4.55u);
draw (5.55u,4.3u)--(5.55u,2u);
draw (5u,4u)--(5.3u,4.3u);
drawarrow (1.5u,2u)--(3.5u,2u);

label.top("a",(2.5u,2u));
label("m",(1.5u,4.5u));
label("m",(1.5u,4.5u)) shifted (4u,-3u);
endfig;
verbatimtex
\end{document}
etex
 
end;