(((# make)(# mon)(# left0)
(
 (*make?[left](# right)
	(mon![left,right] | make![right]))
| 
 (*make?[left](mon![left,left0]))
| 
 make![left0]
| 
 (*mon?[prev,next]
	(*prev?[](# crit)
		( crit![] 
		| (crit?[]next![]))
	))
| left0![]
)))