1  x  x  x
  1  x  x  x
  2  x  x  x
  2  x  x  x
  2  1  x  x
  2  1  x  x
  2  2  x  x
  2  2  x  x
  2  2  1  x
  2  2  1  x
  2  2  2  x
  2  2  2  x
  2  2  2  1
  2  2  2  1
  2  2  2  2
  2  2  2  2