3.0 1 b a a a x b b a a x 2 a b b b x b b b a x 3 a b b b x b b a a x 1 2 3 5 1 2 a 1 1 1 1 0 0 0 2 0 0 0 0 0 0 1 0 0 0 0 0 1 0 1 0 0 0 1 b 1 1 0 1 1 1 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 2 3 Example 21