\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(40, 8)(0,-4)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=3}
    \thinlines
    \node[Nmarks=if,iangle=90,fangle=90](A0)(0,0){$0$}
    \node(A1)(20,0){$1$}
    \node(A2)(40,0){$2$}
    \drawloop[loopangle=180](A0){$0$}
    \drawloop[loopangle=0](A2){$1$}
    \gasset{curvedepth=4}
    \drawedge(A0,A1){$1$}
    \drawedge(A1,A0){$1$}
    \drawedge(A1,A2){$0$}
    \drawedge(A2,A1){$0$}
    \end{picture}
  \end{center}
  \caption{Multiples de 3.}
\end{figure}