-- Math Functions - Standard Deviation

import Control.Monad
import Control.Applicative

main :: IO()
main = do
  n <- readLn
  when (n > 0) $ do
    xs <- map read . words <$> getLine
    putStrLn . show $ sd n xs
    main

sd :: Double -> [Double] -> Double
sd n xs = sqrt . (/ n) . sum . map ((^2) . (subtract m)) $ xs
  where m = sum xs / n

