ALGOIT(T)
ST=STX=LAST=NIL
ct=t
while(ct!=NIL || st!=NIL)do
	if(ct!=NIL)then
		ret=1
		x=ct->key%2
		st=push(st,ct)
		stx=push(stx,x)
		ct=ct->dx
	else
		ct=top(st); x=top(stx)
		if(last!=ct->sx && ct->sx!=NIL)then
			a=val
			x=a+x
			pop(stx)
			stx=push(stx,x)
			ct=ct->sx
		else
			if(ct->sx=NIL)then
				x=a+x
				y=1
				ret=x*y*ct->key
				last=ct
				ct=NIL
				pop(st,x)
			else
				y=val
				ret=top(stx)*y*ct->key
				last=ct
				ct=NIL
				pop(st,x) //abbreviato sto poppando sia st che x
return ret