{[[[[pop 0 =] popd succ                         ] 
  [[null    ] pop pred 1 ack                    ] 
              [[dup pred swap] dip pred ack ack]] cond] 	`ack	def;}


[0=]			z:
[1+]			s:
[1_+]			p:
[\$Z!@\]		b:
[\S!@%\]		c:
[$Z!]			d:
[%%P!1A!1]		e:
[[$P!\](P!A!A!]		f:
[B!$C?~[D!$E?~F?]?]	a:

2 3 A!