import Control.Applicative
import Control.Monad
import Text.Printf

main :: IO ()
main = do
  n <- readLn :: IO Double

  when (n > 0) $ do
    s <- map read . words <$> getLine :: IO [Double]
    let
      m = sum s/n
    
    printf "%.8f\n" $ sqrt $ sum (map (\x -> (x-m)**2) s)/n

    main