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


solve :: [Float] -> Float
solve xs = foldl (\acc x -> (acc + x) / 2) acc zs
    where acc = head ys
          ys = sort xs
          zs = tail ys

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