1
1
1
1
1
2
3
4
5
6
B
B
C
C
C
D
D
D
D
D
D
E
E
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F