\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(40, 36)(0,-6)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=0}
    \thinlines
    \node[Nmarks=i,iangle=180](A11)(0,15){$1,1$}
    \node[Nmarks=f,fangle=270](A22)(20,15){$2,2$}
    \node[Nmarks=f,fangle=0](A23)(40,15){$2,3$}
    \node(A21)(20,0){$2,1$}
    \node(A13)(0,0){$1,3$}
    \node(A12)(0,30){$1,2$}
    \drawloop[loopangle=90](A22){$b$}
    \drawedge(A11,A22){$a$}
    \drawedge(A22,A23){$b$}
    \drawedge[ELside=r](A13,A21){$a$}
    \drawedge(A13,A11){$a$}
    \drawedge(A11,A12){$a$}
    \end{picture}
  \end{center}
  \caption{Un automate reconnaissant $L\cap L'$.}
\end{figure}