let pow x n m =
  let rec doit x n acc =
    if n = 0 then acc
    else if n mod 2 = 0 then doit (x * x mod m) (n / 2) acc
    else doit (x * x mod m) (n / 2) (acc * x mod m) in
  doit x n 1

let pow x n m =
  let rec doit x n acc =
    if n = 0 then acc
    else doit (x * x mod m) (n / 2) (if n mod 2 = 0 then acc else acc * x mod m) in
  doit x n 1

let prime_p n =
  if n == 2 then true
  else if n < 2 || n mod 2 = 0 then false
  else if pow 2 (n - 1) n = 1 then true
  else false

let () =
  let k = read_int () in
  print_endline (if prime_p k then "0" else "0.0277777777777777778")