import qualified Data.Text as T
import qualified Data.Text.IO as T
import qualified Data.Text.Read as T

main :: IO ()
main = do
  (n  : _) <- map (unsafeSignedDecimal) . T.words <$> T.getLine :: IO [Int]
  let
    r = n `mod` 2
  print (fromRational $ (1 / 2) + (toRational r / toRational n) :: Double)

unsafeSignedDecimal :: T.Text -> Int
unsafeSignedDecimal s = case T.signed T.decimal s of
  Right (n, _) -> n
