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