\begin{figure}[!h]
\setlength{\unitlength}{.9cm}

\begin{center}
\begin{picture}(9,9)(0,0) \label{fig-sol4}
\linethickness{.1pt}

\multiput(3,2)(1,0){3}{\circle{.3}} \multiput(3,2)(1,0){3}{\circle*{.2}}

\multiput(3,3)(1,0){3}{\circle{.3}} \multiput(3,3)(1,0){3}{\circle*{.2}}

\multiput(1,4)(1,0){7}{\circle{.3}} \multiput(1,4)(1,0){7}{\circle*{.2}}

\multiput(1,5)(1,0){7}{\circle{.3}} \multiput(1,5)(1,0){7}{\circle*{.2}}

\multiput(1,6)(1,0){7}{\circle{.3}} \multiput(1,6)(1,0){7}{\circle*{.2}}

\multiput(3,7)(1,0){3}{\circle{.3}} \multiput(3,7)(1,0){3}{\circle*{.2}}

\multiput(3,8)(1,0){3}{\circle{.3}} \multiput(3,8)(1,0){3}{\circle*{.2}}

\put(0,5){\line(1,0){8}} \put(7.5,5){\vector(1,0){1}} \put(8,5.2){x}

\put(4,1){\line(0,1){8}} \put(4,8.5){\vector(0,1){1}} \put(4.2,9){y}


\put(2.5,1.5){\line(0,1){2}} \put(2.5,3.5){\line(-1,0){2}} \put(.5,3.5){\line(0,1){3}}
\put(.5,6.5){\line(1,0){2}} \put(2.5,6.5){\line(0,1){2}} \put(2.5,8.5){\line(1,0){3}}
\put(5.5,8.5){\line(0,-1){2}} \put(5.5,6.5){\line(1,0){2}} \put(7.5,6.5){\line(0,-1){3}}
\put(7.5,3.5){\line(-1,0){2}} \put(5.5,3.5){\line(0,-1){2}} \put(5.5,1.5){\line(-1,0){3}}



\put(0,5){\line(1,-1){4}} \put(0,6){\line(1,-1){5}} \put(0,7){\line(1,-1){6}} \put(1,7){\line(1,-1){5}}
\put(2,7){\line(1,-1){4}} \put(2,8){\line(1,-1){5}} \put(2,9){\line(1,-1){6}} \put(3,9){\line(1,-1){5}}
\put(4,9){\line(1,-1){4}}

\put(9,3){\vector(-1,0){1}} \put(9.1,2.9){$x+y=2$}

\put(8,2){\vector(-2,1){2}} \put(8.1,1.9){$x+y=0$}

\put(7,1){\vector(-1,0){1}} \put(7.1,.9){$x+y=-2$}

\end{picture}
\end{center}
\end{figure}
