Create a new list form every n-th item of a branch

Hello,

I'm working on definition in which I've list with the following structure:

####branch 1

1

1

1

1

####branch 2

2

2

2

2

####branch 3

3

3

3

3

##### etc...

Can anyone help in how I get this list structure:

####branch 1

1

2

3

4

####branch 2

1

2

3

4

####branch 3

1

2

3

4

##### etc...

Think it must be simple but I've no idea how to make it?

k.