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