Getting column data and re-arranging it in rows, with a pattern, using formulas

In a worksheet of multiple sheets, I have Sheet1, e.g. with the following: (these rows will be less or more and are manually entered)

Sheet1

        A           B       C       1       APPLE       ORANGE  LEMON   2       bravo       chair   mars    3       charlie     table   jupiter 4       alpha       box     venus   5       delta               saturn  6       foxtrot                     

I would like some help in constructing 'Sheet2' via formulas so that it rearranges data from Sheet1 as follows

Sheet2 (Desired result)

        A       B       1       APPLE           2               bravo   3               charlie 4               alpha   5               delta   6               foxtrot 7                       8       ORANGE          9               chair   10              table   11              box     12                      13      LEMON           14              mars    15              jupiter 16              venus   17              saturn  

It probably needs some combination of ARRAYFORMULA(), TRANSPOSE and INDEX but I need some help with getting them into lesser columns (and more rows.) as shown. Please note that Sheet1's data will keep changing in number of rows (or columns) so Sheet2 needs to adapt to that.

Thank you.