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