\documentclass[11pt]{report}
\input{header}
\pagestyle{empty}
\begin{document}
\psscalebox{1.8}{\arrset{1}%
  \begin{pspicture}(-1,-1)(6,7)
    \arraxes(0,0)(-1,-1)(6,7)
    \arrMainVertex(1,1){a}
    \arrMainVertex(1,6){b}
    \arrMainVertex(5,1){c}
    \arrMainVertex(5,6){d}
    \arrMinorVertex(1,3){1}\uput[-45]{0}(1,3){$v_1$}
    \arrMinorVertex(5,3){2}\uput[225]{0}(5,3){$v_2$}
    \arrMinorVertex(1,4){3}
    \arrMinorVertex(5,4){4}
    \ncline[linewidth=0.5pt,linecolor=blue]{a}{1}
    \ncline[linewidth=0.5pt,linecolor=blue]{c}{2}
    \ncline[linewidth=0.5pt,linecolor=blue]{3}{b}\Aput[1pt]{$s_3$}
    \ncline[linewidth=0.5pt,linecolor=blue]{4}{d}\Bput[1pt]{$s_4$}
    \ncline[linestyle=dashed,linewidth=0.5pt,linecolor=blue]{1}{2}\Bput[1pt]{$s_1$}
    \ncline[linestyle=dashed,linewidth=0.5pt,linecolor=blue]{3}{4}\Aput[1pt]{$s_2$}
    \ncline[linewidth=0.5pt,linecolor=blue]{1}{3}
    \ncline[linewidth=0.5pt,linecolor=blue]{2}{4}
  \end{pspicture}
}
\end{document}
