A
A
A
B
B
B
B
A
A
A
B
B
B
B
A
A
A
B
B
B
B
A
A
A
B
B
B
A
A
A
B
B
B
A
A
A
B
B
B
A
A
A
B
B
B
A
A
A
B
B
B