6 538 ( 552 ) (1) () (2) () ( )( ) 1
vs () (1) (2) () () () ) ()() (3) () ( () 2
() () () ()( ) () (7) (8) () 3
4
5
abc b c 6
a (a) b b ()() 7
c (c) ()() 8
9
10
() 1 ()()() 2 () 3 1 1052 1051 () 1053 11