return [ [ 2, 3, 4, 5 ], [ 1, 6, 7, 3 ], [ 1, 2, 8, 9 ], [ 1, 9, 10, 11 ], 
  [ 1, 11, 12, 6 ], [ 2, 5, 13, 14 ], [ 2, 14, 15, 8 ], [ 3, 7, 16, 17 ], 
  [ 3, 17, 18, 4 ], [ 4, 18, 19, 11 ], [ 4, 10, 20, 5 ], [ 5, 20, 21, 13 ], 
  [ 6, 12, 22, 14 ], [ 6, 13, 23, 7 ], [ 7, 23, 24, 16 ], [ 8, 15, 25, 26 ], 
  [ 8, 26, 27, 9 ], [ 9, 27, 28, 10 ], [ 10, 28, 29, 20 ], [ 11, 19, 30, 12 ],
  [ 12, 30, 31, 22 ], [ 13, 21, 31, 23 ], [ 14, 22, 32, 15 ], 
  [ 15, 32, 33, 25 ], [ 16, 24, 34, 26 ], [ 16, 25, 35, 17 ], 
  [ 17, 35, 36, 18 ], [ 18, 36, 29, 19 ], [ 19, 28, 37, 30 ], 
  [ 20, 29, 38, 21 ], [ 21, 38, 32, 22 ], [ 23, 31, 33, 24 ], 
  [ 24, 32, 38, 34 ], [ 25, 33, 37, 35 ], [ 26, 34, 36, 27 ], 
  [ 27, 35, 37, 28 ], [ 29, 36, 34, 38 ], [ 30, 37, 33, 31 ] ];
