\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(35, 26)(0,-13)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=0}
    \thinlines
    \node[Nmarks=if,iangle=180,fangle=180](A0)(0,0){}
    \node[Nmarks=f,fangle=90](A1)(15,10){}
    \node[Nmarks=f,fangle=90](A2)(35,10){}
    \node(A3)(15,-10){}
    \node[Nmarks=f,fangle=0](A4)(35,-10){}
    \drawedge(A0,A1){$a$}
    \drawedge[ELside=r](A0,A3){$b$}
    \drawloop[loopangle=0](A2){$a$}
    \gasset{curvedepth=3}
    \drawedge(A1,A2){$a$}
    \drawedge(A2,A1){$b$}
    \drawedge(A3,A4){$a$}
    \drawedge(A4,A3){$b$}
    \end{picture}
  \end{center}
  \caption{L'automate minimal de $L$.}
\end{figure}