import Data.List
import Text.Printf

main :: IO ()
main = do
    n <- readLn
    xs <- map read . words <$> getLine
    let x = solve n xs
    printf "%.1f" x

solve :: Int -> [Int] -> Float
solve n as
    | odd n     = fromIntegral ((sort as) !! (n `div` 2))
    | otherwise = (fromIntegral ((sort as) !! ((n `div` 2) - 1)) + fromIntegral ((sort as) !! (n `div` 2)) ) / 2.0