span align="justify"> 3 S 4 span> a 1 0001a 2 (Y 1 ) 0010x 1 S 3 R 4 a 1 0001a < span align = "justify"> 3 (Y 2 ) 0011 S 3 a 2 a 3 0010 0011a 4 (Y 3 ) 0100 < span align = "justify"> 01001S 2 R 3 S 2 R 3 R 4 a 4 0100a 5 (Y 4 ) 01011S 4 a 5 0101a 6 (Y 5 ) 0110x 2 S 3 R 4 a 5 0101a 7 (Y 12 ) 0111 S < span align = "justify"> 3 a 6 a 12 0110 1100a 8 ( Y 6 ) 1000 10001S 1 R 2 R ...