A	B
A	C
A	D
B	C
B	D
C	D
C	E
C	F
C	G
D	E
D	G
E	F
E	H
F	G
F	H
G	J
H	I
H	L
H	K
H	M
I	J
I	L
I	K
I	M
J	N
K	L
K	M
L	M
M	O
M	N
N	P
O	Q
O	R
Q	R
Q	S
Q	T
R	S
R	T
S	T