red or black
1
r
2
b
3
r
4
b
5
r
6
b
7
r
8
b
9
r
10
b
11
b
12
r
13
b
14
r
15
b
16
r
17
b
18
r
19
r
20
b
21
r
22
b
23
r
24
b
25
r
26
b
27
r
28
b
29
b
30
r
31
b
32
r
33
b
34
r
35
b
36
r
r
b
r
b
r
b
r
b
r
b
b
r
b
r
b
r
b
r
r
b
r
b
r
b
r
b
r
b
b
r
b
r
b
r
b
r