LR

DGA = (DGB, XXX)
DGB = (XXX, DGZ)
DGZ = (DGB, XXX)
EHA = (EHB, XXX)
EHB = (EHC, EHC)
EHC = (EHZ, EHZ)
EHZ = (EHB, EHB)
XXX = (XXX, XXX)