R a 1 0 # 1 a # 1 R 1 b R 1 # 1 c 2 # R 2 a 3 # R 3 a 3 # R 3 b 3 # R 0 b 4 # R 4 a 4 # R 4 b 4 # R 4 c 5 # R 5 b 6 # R 6 a 6 # R 6 b 6 # R