import Control.Applicative ((<$>))
import Data.List

main :: IO ()
main = do
  n <- getl $ read
  solve n <$> getl (map read . words) >>= print

solve :: Int -> [Int] -> Double
solve n xs = f $ sort xs
  where
    f :: [Int] -> Double
    f ys | odd n = fromIntegral . head . snd $ splitAt (n `div` 2) ys
         | otherwise = (/ 2) . fromIntegral . sum . take 2 . snd $ splitAt (n `div` 2 - 1) ys

getl :: (String -> a) -> IO a
getl f = f <$> getLine