Method 2: The exclusion method is always * * A66, A, B and C together, and then completely arranged, A33*A44, A, B and C together, C32, and then arranged into a whole A22, which is equivalent to five, and two of them (and then a whole A22) cannot be arranged together, so the arrangement method is, A55-
It is strongly recommended not to exclude methods, which is not suitable for this topic.