\documentclass[10pt]{article} \usepackage{pstricks-add} \pagestyle{empty} \begin{document} \newrgbcolor{xdxdff}{0.49 0.49 1} \psset{xunit=1.0cm,yunit=1.0cm,algebraic=true,dotstyle=o,dotsize=3pt 0,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25} \begin{pspicture*}(-5.76,-3.39)(5.21,4.92) \psline(-2,-1)(2,-1) \psline[linestyle=dashed,dash=2pt 2pt](-2,-1)(0,1) \psline[linestyle=dashed,dash=2pt 2pt](0,1)(4,1) \psline(4,1)(2,-1) \psline[linestyle=dashed,dash=2pt 2pt](-1,0)(-1,4) \psline(-1,4)(-2,-1) \psline[linestyle=dashed,dash=2pt 2pt](-1,4)(0,1) \psline(-1,4)(2,-1) \psline(-1,4)(4,1) \psline[linestyle=dashed,dash=2pt 2pt](0,1)(2,-1) \psline[linestyle=dashed,dash=2pt 2pt](-2,-1)(4,1) \psdots[dotstyle=*,linecolor=blue](-2,-1) \rput[bl](-2.24,-1.01){\blue{$A$}} \psdots[dotstyle=*,linecolor=blue](2,-1) \rput[bl](2.2,-1.08){\blue{$B$}} \psdots[dotstyle=*,linecolor=xdxdff](0,1) \rput[bl](0.05,1.08){\xdxdff{$D$}} \psdots[dotstyle=*,linecolor=blue](4,1) \rput[bl](4.06,1.08){\blue{$C$}} \psdots[dotstyle=*,linecolor=xdxdff](-1,0) \rput[bl](-1.16,0.1){\xdxdff{$I$}} \psdots[dotstyle=*,linecolor=blue](-1,4) \rput[bl](-0.94,4.08){\blue{$S$}} \psdots[dotstyle=*,linecolor=darkgray](1,0) \rput[bl](0.94,0.2){\darkgray{$O$}} \end{pspicture*} \end{document}