import math



while True:

    n = int(eval(input()))

    if 0 == n:

        break



    points = list(map(int, input().split(' ')))



    m = sum(points)/n

    s = math.sqrt(sum([ (s - m)**2 for s in points ])/n)



    print(('{:.5f}'.format(s)))
from math import sqrt



def sd(nums):

    n   = len(nums)

    ave = sum(nums)/n



    return abs(sqrt(sum([(s - ave)**2 for s in nums])/n))



def main():

    while True:

        n = eval(input())



        if n == '0':

            break



        nums = [int(x) for x in input().split()]

        print(("{:f}".format(sd(nums))))



if __name__ == '__main__':

    main()

import math

while True:
    n = int(eval(input()))
    if 0 == n:
        break
    points = list(map(int, input().split(" ")))
    m = sum(points) / n
    s = math.sqrt(sum([(s - m) ** 2 for s in points]) / n)
    print(("{:.5f}".format(s)))

from math import sqrt


def sd(nums):
    n = len(nums)
    ave = sum(nums) / n
    return abs(sqrt(sum([(s - ave) ** 2 for s in nums]) / n))


def main():
    while True:
        n = eval(input())
        if n == "0":
            break
        nums = [int(x) for x in input().split()]
        print(("{:f}".format(sd(nums))))


if __name__ == "__main__":
    main()

-import math +from math import sqrt -while True: -    n = int(eval(input())) -    if 0 == n: -        break -    points = list(map(int, input().split(" "))) -    m = sum(points) / n -    s = math.sqrt(sum([(s - m) ** 2 for s in points]) / n) -    print(("{:.5f}".format(s))) + +def sd(nums): +    n = len(nums) +    ave = sum(nums) / n +    return abs(sqrt(sum([(s - ave) ** 2 for s in nums]) / n)) + + +def main(): +    while True: +        n = eval(input()) +        if n == "0": +            break +        nums = [int(x) for x in input().split()] +        print(("{:f}".format(sd(nums)))) + + +if __name__ == "__main__": +    main()