from statistics import mean

import math

ans = []

while 1:

  n = int(eval(input()))

  if n == 0: break

  l = list(map(int, input().split()))

  m = mean(l)

  print(("{0:.8f}".format(math.sqrt(sum([(s - m) ** 2 for s in l]) / n))))

while eval(input()) != "0":

  l = list(map(int, input().split()))

  print(("{0:.8f}".format((sum([(s - sum(l) / len(l)) ** 2 for s in l]) / len(l)) ** 0.5)))

from statistics import mean
import math

ans = []
while 1:
    n = int(eval(input()))
    if n == 0:
        break
    l = list(map(int, input().split()))
    m = mean(l)
    print(("{0:.8f}".format(math.sqrt(sum([(s - m) ** 2 for s in l]) / n))))

while eval(input()) != "0":
    l = list(map(int, input().split()))
    print(
        (
            "{0:.8f}".format(
                (sum([(s - sum(l) / len(l)) ** 2 for s in l]) / len(l)) ** 0.5
            )
        )
    )

-from statistics import mean -import math - -ans = [] -while 1: -    n = int(eval(input())) -    if n == 0: -        break +while eval(input()) != "0": -    m = mean(l) -    print(("{0:.8f}".format(math.sqrt(sum([(s - m) ** 2 for s in l]) / n)))) +    print( +        ( +            "{0:.8f}".format( +                (sum([(s - sum(l) / len(l)) ** 2 for s in l]) / len(l)) ** 0.5 +            ) +        ) +    )