while True:

    number_of_input = int(input())

    if number_of_input == 0:

        break

    values = [float(x) for x in input().split()]

    second_moment = sum([x * x for x in values]) / number_of_input

    first_moment = sum([x for x in values]) / number_of_input

    print((second_moment - first_moment ** 2.0) ** 0.5)
import math



while True:

    number_of_input = int(input())

    if number_of_input == 0:

        break

    values = [float(x) for x in input().split()]

    second_moment = sum([x ** 2.0 for x in values]) / number_of_input

    first_moment = sum([x for x in values]) / number_of_input

    print(math.sqrt(second_moment - first_moment ** 2.0))
while True:
    number_of_input = int(input())
    if number_of_input == 0:
        break
    values = [float(x) for x in input().split()]
    second_moment = sum([x * x for x in values]) / number_of_input
    first_moment = sum([x for x in values]) / number_of_input
    print((second_moment - first_moment**2.0) ** 0.5)

import math

while True:
    number_of_input = int(input())
    if number_of_input == 0:
        break
    values = [float(x) for x in input().split()]
    second_moment = sum([x**2.0 for x in values]) / number_of_input
    first_moment = sum([x for x in values]) / number_of_input
    print(math.sqrt(second_moment - first_moment**2.0))

+import math + -    second_moment = sum([x * x for x in values]) / number_of_input +    second_moment = sum([x**2.0 for x in values]) / number_of_input -    print((second_moment - first_moment**2.0) ** 0.5) +    print(math.sqrt(second_moment - first_moment**2.0))