import sys

 

mode = 0

for line in sys.stdin:

    if mode == 0:

        n = int(line.strip('\n'))

        if n == 0: break

        mode = 1

    elif mode == 1:

        x = [float(i) for i in line.strip('\n').split()]

        ave = sum(x) / n

        std = (sum([(i-ave)**2 for i in x])/n)**0.5

        print(std)

        mode = 0
while True:

    n = int(input())

    if n == 0: break



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

    ave = sum(x) / float(n)

    std = (sum([(e-ave)**2 for e in x])/n)**0.5

    print(std)
import sys

mode = 0
for line in sys.stdin:
    if mode == 0:
        n = int(line.strip("\n"))
        if n == 0:
            break
        mode = 1
    elif mode == 1:
        x = [float(i) for i in line.strip("\n").split()]
        ave = sum(x) / n
        std = (sum([(i - ave) ** 2 for i in x]) / n) ** 0.5
        print(std)
        mode = 0

while True:
    n = int(input())
    if n == 0:
        break
    x = list(map(int, input().split()))
    ave = sum(x) / float(n)
    std = (sum([(e - ave) ** 2 for e in x]) / n) ** 0.5
    print(std)

-import sys - -mode = 0 -for line in sys.stdin: -    if mode == 0: -        n = int(line.strip("\n")) -        if n == 0: -            break -        mode = 1 -    elif mode == 1: -        x = [float(i) for i in line.strip("\n").split()] -        ave = sum(x) / n -        std = (sum([(i - ave) ** 2 for i in x]) / n) ** 0.5 -        print(std) -        mode = 0 +while True: +    n = int(input()) +    if n == 0: +        break +    x = list(map(int, input().split())) +    ave = sum(x) / float(n) +    std = (sum([(e - ave) ** 2 for e in x]) / n) ** 0.5 +    print(std)