0	 0 0 1 1 1 2 2 2
     1	 0 0 1 1 1 2 3 3
     2	 0 1 2 2 2 3 4 4
     3	 0 1 2 2 2 3 4 5
     4	 0 1 2 3 4 5 6 6
     5	 0 1 2 3 4 5 6 7