..X X 2 3 7B) Đ S2 2 5( 1) ( 3) 2 ...X X X ...
1
...
x
x
2
3
7
b)
Đ
S
2
2
5
(
1)
(
3)
2
...
x
x
x
7
c)
1
...
x
x
2
3
7
b)
Đ
S
2
2
5
(
1)
(
3)
2
...
x
x
x
7
c)