Adding 1

Front 1

0+1

Back 1

1

Front 2

1+1=

Back 2

2

Front 3

2+1=

Back 3

3

Front 4

3+1=

Back 4

4

Front 5

4+1=

Back 5

5

Front 6

5+1=

Back 6

6

Front 7

6+1=

Back 7

7

Front 8

7+1=

Back 8

8

Front 9

8+1=

Back 9

9

Front 10

9+1=

Back 10

10

Front 11

10+1=

Back 11

11

Front 12

11+1=

Back 12

12

Front 13

12+1=

Back 13

13

Front 14

13+1=

Back 14

14

Front 15

14+1=

Back 15

15

Front 16

15+1=

Back 16

16

Front 17

16+1=

Back 17

17

Front 18

17+1=

Back 18

18

Front 19

18+1=

Back 19

19

Front 20

19+1=

Back 20

20