$$\begin{array}{ccccc}A& \stackrel{}{\to }& B& \stackrel{}{\leftarrow }& C\\ \uparrow & & 0\uparrow & & \uparrow 1& \\ D& \stackrel{2}{\to }& E& \stackrel{3}{\leftarrow }& F\\ \downarrow & & 4\downarrow & & \downarrow 5& \\ G& \underset{6}{\overset{}{\to }}& H& \underset{7}{\overset{}{\leftarrow }}& I\\ \parallel & & & & \parallel & \\ J& =& K& =& L\end{array}$$