Bmi1 -> Bmi1ubd Bmi1ubd -> Bmi1 R1B -> R1Bubd R1Bubd -> R1B Bmi1 + R1B -> Z Z -> Bmi1 + R1B Z -> Zub Zub -> Z Zub -> Bmi1 + R1Buba Bmi1 + R1Buba -> Zub R1B -> R1Bub R1Bub -> R1B R1Buba -> R1B H2A -> H2Auba H2Auba -> H2A 0 -> R1B R1Bubd -> 0 0 -> Bmi1 Bmi1ubd -> 0