a

a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a

b

a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a

c

a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a

d

a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a

e

a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a