gap> Y:=ClassifyingSpaceFiniteGroup(CyclicGroup(2),9);
Regular CW-complex of dimension 9
gap> Size(Y);
29524
gap> CriticalCells(Y);
[ [ 9, 1 ], [ 8, 124 ], [ 7, 1215 ], [ 6, 1246 ], [ 5, 487 ], [ 4, 254 ], 
  [ 3, 117 ], [ 2, 54 ], [ 1, 9 ], [ 0, 10 ] ]
