$$\begin{array}{ccc}\hfill H\hfill & \hfill \to \hfill & \hfill G\hfill \\ \hfill \downarrow \hfill & \hfill \hfill & \hfill \downarrow \hfill \\ \hfill K\hfill & \hfill \to \hfill & \hfill L\hfill \end{array}$$