Graph figure with LaTeX/Tikz

graph.tex

\begin{tikzpicture}
     \tikzstyle{node_style} = [circle,draw=black]
     \tikzstyle{edge_style} = [draw=black]
     \node[node_style] (v1) at (-2,2) {2};
     \node[node_style] (v2) at (2,2) {3};
     \node[node_style] (v3) at (4,0) {6};
     \node[node_style] (v4) at (2,-2) {4};
     \node[node_style] (v5) at (-2,-2) {5};
     \node[node_style] (v6) at (-4,0) {1};
     \draw[edge_style]  (v1) edge (v2);
     \draw[edge_style]  (v2) edge (v3);
     \draw[edge_style]  (v3) edge (v4);
     \draw[edge_style]  (v4) edge (v5);
     \draw[edge_style]  (v5) edge (v6);
     \draw[edge_style]  (v6) edge (v1);
     \draw[edge_style]  (v5) edge (v1);
     \draw[edge_style]  (v5) edge (v2);
     \draw[edge_style]  (v4) edge (v2);
\end{tikzpicture}