
import Control.Monad
import Data.List

solve  :: [Double] -> Double
solve [] = 0
solve (a:as) | as == [] = a
             | otherwise = solve ([(a + (head as)) / 2] ++ (tail as))

main = do
    n <- readLn :: IO Int
    vi <- map (\x -> fromRational $ toRational $ (read x) :: Double)  . words <$> getLine
    print $ solve (sort vi)
