import Control.Applicative

main = do xs <- map read . concatMap words . lines <$> getContents
          putStr . unlines . map show $ solve xs

solve :: [Int] -> [Double]
solve (0:_) = []
solve (n:xs) = sig : solve rest
        where (ss,rest) = splitAt n xs
              ss' = map fromIntegral ss
              n' = fromIntegral n
              m = (sum ss') / n' :: Double
              sig = sqrt $ (sum [(x-m)**2.0| x<-ss'])/n' :: Double
          