import Data.Ratio
import Data.List (sort)

main = do
  getLine
  li <- getLine
  let as = map read $ words li
  let ans = compute as
  print ans

compute :: [Integer] -> Double
compute as = fromRational $ foldl1 f $ map fromIntegral $ sort as

f :: Rational -> Rational -> Rational
f x y = (x+y) / 2