b
f
d
b
f
a
a
c
a
d
d
f
e
f
a
c
a
c
e
c
a
c
b
b
d
b
c
f
c
d
a
d
c
f
c
b
b
b
b
d
d
a
f
c
e
e
g
f
c
e
b
b
b
b
a
b
a
g
b
c
c
c
b
a
a
a
b
a
d
b
c
b
b
f
d
f
f
b
f
b