\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(25, 29)(0,-4)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=3}
    \thinlines
    \node[Nmarks=i,iangle=270](A0)(12.5,0){$0$}
    \node(A1)(0,20){$1$}
    \drawloop[loopangle=180](A1){$a$}
    \node[Nmarks=f,fangle=90](A2)(25,20){$2$}
    \drawloop[loopangle=0](A2){$b$}
    \gasset{curvedepth=4}
    \drawedge(A1,A2){$b$}
    \drawedge(A2,A1){$a$}
    \drawedge(A0,A1){$a$}
    \gasset{curvedepth=-4}
    \drawedge[ELside=r](A0,A2){$b$}
    \end{picture}
  \end{center}
  \caption{L'automate standardisé.}
\end{figure}