ROPI DOPI 

After interference over the Blackwood or Gerber (or any other asking bid) 
ask, a 	(Re)Double = 0 aces
	Pass   = 1 ace
	next bid = 2 aces
	etc

Example:
	part	opp	you
	4NT 	5S	x = 0 aces
			p = 1 ace
			5NT = 2 aces 
			6C = 3 aces

	4C	x	xx = 0 aces
			p = 1 ace
			4D = 2 aces
			4H = 3 aces


OTHER similar conventions are 
	PODI PORI where pass = 0 and (re)double = 1 

	REPO DEPO where pass = odd (1 or 3) and (re)double = even (0 or 2)