How can pyramid structures be split into two sets of small pyramids (with illustrations in them)?

Similarly, this is a 30-person pyramid structure with no spire, which now needs to be split from the red Line into two small pyramids.

These 30 people are traversed from the database, in chronological order from top to bottom from left to right.

Originally I was thinking of splitting with single-or dual-even, but the single-even split is not split from the red line, but splits each other, and then makes all the singular and even-numbered two new pyramids. But such single-and-odd-numbered is not split from the red line.

Don't know what to do with a split like this on the train of thought?

Reply to discussion (solution)

$a = array (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30); Echo '; for ($i =0, $n = 2; $i
 
 

  ';} Echo '; for ($i =0, $n =2; $i
  
 

   '; Echo '; Echo '; foreach ($l as $v) echo join (', $v), '
   
'; Echo ';
  
 

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