import Prelude
import Data.List (sort, genericLength)

main :: IO ()
main = do
  n <- read <$> getLine
  as <- map read . words <$> getLine
  print $ calc n as

calc :: Int -> [Int] -> Double
calc n as = let as' = sort as
            in  if odd n then fromIntegral $ as' !! div n 2
                         else average $ take 2 $ drop (div n 2 - 1) as

average :: (Real a, Fractional b) => [a] -> b
average is = realToFrac (sum is) / genericLength is