LR

GGA = (GGB, XXX)
GGB = (XXX, GGZ)
GGZ = (GGB, XXX)
HHA = (HHB, XXX)
HHB = (HHC, HHC)
HHC = (HHZ, HHZ)
HHZ = (HHB, HHB)
XXX = (XXX, XXX)