import Data.List -- to use sort

main = do
  n <- readLn :: IO Int
  as <- (map read . words) <$> getLine
  let n' = n `div` 2
  let as' = sort as :: [Double]
  putStrLn . show $ if odd n then as' !! n' else ((as' !! (n' - 1)) + (as' !! n')) / 2