cf_rule0(0).
cf_rule1a(1,c,2).
cf_rule1a(0,c,2).
cf_rule1a(2,c,1).
cf_rule1a(1,b,2).
cf_rule1a(0,b,1).
cf_rule1a(2,b,0).
cf_rule1a(2,a,1).
cf_rule1a(0,a,1).