Size_Group[ BLOCK_SIZES ] =
{
  0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3,
  3, 3, 3, 3, 3, 3, 3, 3, 0, 0, 1, 1, 2, 2,
  1, 1, 2, 2
}