import Control.Applicative
import Control.Monad
import Data.List

rec :: [Float] -> Float
rec [x] = x
rec (x:y:xs) = rec (z:xs)
    where z = (x + y) / 2

solve :: [Float] -> Float
solve = rec . sort

main :: IO ()
main = do
    _ <- getLine
    line <- map read . words <$> getLine
    print $ solve line
