Adding

Front 1

1+1

Back 1

2

Front 2

19+1

Back 2

20

Front 3

10+1

Back 3

11

Front 4

17+1

Back 4

18

Front 5

6+1

Back 5

7

Front 6

4+1

Back 6

5

Front 7

2+1

Back 7

3

Front 8

9+1

Back 8

10

Front 9

8+1

Back 9

9

Front 10

12+1

Back 10

13

Front 11

11+1

Back 11

12

Front 12

18+1

Back 12

19

Front 13

13+1

Back 13

14

Front 14

7+1

Back 14

8

Front 15

5+1

Back 15

6

Front 16

14+1

Back 16

15

Front 17

3+1

Back 17

4

Front 18

15+1

Back 18

16