C
A
D
A
C
B
B
D
D
A
C
C
C
B
D
C
B
D
B
B
D
A
A
B
C
B
A
B
D
B
A
C
C
D
A
A
B
B
B
A
B
A
A
B
B
B
A
A
A
B
B
B
A
B
A
A