1	A
1	B
2	C
2	D
3	E
4	F
4	G
5	H
5	I
6	J
7	K
7	L
8	M
9	N
9	O
10	P
11	Q
11	R
12	S
12	T
13	U
14	V
14	W
15	X
16	Y
16	Z
17	AA
18	AB
18	AC
19	AD
20	AE