while 1:

 n=int(eval(input()))

 if n==0:break

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

 print(((sum([(m-sum(s)/n)**2 for m in s])/n)**.5))
while 1:

 n=int(eval(input()))

 if n==0:break

 s=input().split()

 a=sum([int(x) for x in s])/n

 print(((sum([int(x)**2 for x in s])/n-a*a)**.5))
while 1:
    n = int(eval(input()))
    if n == 0:
        break
    s = [int(x) for x in input().split()]
    print(((sum([(m - sum(s) / n) ** 2 for m in s]) / n) ** 0.5))

while 1:
    n = int(eval(input()))
    if n == 0:
        break
    s = input().split()
    a = sum([int(x) for x in s]) / n
    print(((sum([int(x) ** 2 for x in s]) / n - a * a) ** 0.5))

-    s = [int(x) for x in input().split()] -    print(((sum([(m - sum(s) / n) ** 2 for m in s]) / n) ** 0.5)) +    s = input().split() +    a = sum([int(x) for x in s]) / n +    print(((sum([int(x) ** 2 for x in s]) / n - a * a) ** 0.5))