0+0; 0+1

Front 1

0+0

Back 1

0

Front 2

0+1

Back 2

1

Front 3

1+1

Back 3

2

Front 4

1+2

Back 4

3

Front 5

2+2

Back 5

4

Front 6

2+3

Back 6

5

Front 7

3+3

Back 7

6

Front 8

3+4

Back 8

7

Front 9

4+4

Back 9

8

Front 10

4+5

Back 10

9

Front 11

5+5

Back 11

10

Front 12

5+6

Back 12

11

Front 13

6+6

Back 13

12

Front 14

6+7

Back 14

13

Front 15

7+7

Back 15

14

Front 16

7+8

Back 16

15

Front 17

8+8

Back 17

16

Front 18

8+9

Back 18

17

Front 19

9+9

Back 19

18

Front 20

9+10

Back 20

19

Front 21

10+10

Back 21

20

Front 22

10+11

Back 22

21