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