return [ [ 2, 3, 4, 5 ], [ 1, 5, 6, 7 ], [ 1, 7, 8, 9 ], [ 1, 9, 10, 11 ], 
  [ 1, 11, 6, 2 ], [ 2, 5, 12, 7 ], [ 2, 6, 13, 3 ], [ 3, 13, 14, 9 ], 
  [ 3, 8, 10, 4 ], [ 4, 9, 14, 11 ], [ 4, 10, 12, 5 ], [ 6, 11, 14, 13 ], 
  [ 7, 12, 14, 8 ], [ 8, 13, 12, 10 ] ];
