import math



while True:

    n = eval(input())

    if n == 0:

        break

    m = list(map(float,input().split()))

    print("%5f" %(math.sqrt(sum([(m[i]-(sum(m)/len(m)))**2 for i in range(n)])/n)))
import math



while True:

    n = eval(input())

    if n == 0:

        break

    m = list(map(float,input().split()))

    ave= sum(m)/len(m)



    print("%5f" %(math.sqrt(sum([(m[i]-(ave))**2 for i in range(n)])/n)))
import math

while True:
    n = eval(input())
    if n == 0:
        break
    m = list(map(float, input().split()))
    print(
        "%5f"
        % (math.sqrt(sum([(m[i] - (sum(m) / len(m))) ** 2 for i in range(n)]) / n))
    )

import math

while True:
    n = eval(input())
    if n == 0:
        break
    m = list(map(float, input().split()))
    ave = sum(m) / len(m)
    print("%5f" % (math.sqrt(sum([(m[i] - (ave)) ** 2 for i in range(n)]) / n)))

-    print( -        "%5f" -        % (math.sqrt(sum([(m[i] - (sum(m) / len(m))) ** 2 for i in range(n)]) / n)) -    ) +    ave = sum(m) / len(m) +    print("%5f" % (math.sqrt(sum([(m[i] - (ave)) ** 2 for i in range(n)]) / n)))