Easy/standard pass to the center.

sdr> heads lead right
| 4B>  3G<  1B>  2G<
| 
| 4G>  3B<  1G>  2B<
sdr> pass to the center
| 3B>  4B>  2G<  1G<
| 
| 3G>  4G>  2B<  1B<
sdr> /exit