( 10  (  (  1  ( (a 2) (c 3) (b 4)   ) )
         (  2  ( (c 5)(b 6)          ) )  
         (  3  ( (d 7)               ) )
         (  4  ( (a 8) (a 9)         ) )
         (  5  5                       )
         (  6  6                       )
         (  7  7                       )
         (  8  8                       )
         (  9  ( (b 10)              ) )
         ( 10  10                      )
      )
)