A

B

A

C

D

D

E

A

B

A

C

E

-

+

+

+

+

+

+

-

-

-

-

-

3

4

k

k

k

k

1

2

3

4

x

x

x

x

1

2

3

4

k

s

a

b

k

a

c

d

k

d

e

a

b

k

a

c  e 

0

0

0

0

0

0

1

1

1

1

1

1

1

2