let () = Scanf.scanf "%d\n" @@ fun n ->
  Printf.printf "%d\n" @@ 
  if n mod 2 = 1
  then 0
  else
    List.fold_right (fun d -> ( + ) @@ n / d)
    [ 10; 50; 250; 1250; 6250; 31250; 156250; 781250; 3906250; 19531250;
      97656250; 488281250; 2441406250; 12207031250; 61035156250;
      305175781250; 1525878906250; 7629394531250; 38146972656250;
      190734863281250; 953674316406250; 4768371582031250; 23841857910156250;
      119209289550781250; 596046447753906250; 2980232238769531250 ] 0
