let () = Scanf.scanf "%d %d %d" @@ fun a b x ->
  Printf.printf "%.12f\n" @@
  if x <= a * a * b / 2
  then 90. -. 45. *. atan2 (2. *. float_of_int x) (float_of_int (a * b * b)) /. atan 1.
  else 90. -. 45. *. atan2 (float_of_int (a * a * a)) (2. *. float_of_int (a * a * b - x)) /. atan 1.
