while True:

    n = int(eval(input()))

    if n == 0:

        break

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

    m = sum(s)/n

    a2 = sum([(s[i] - m)**2 for i in range(n)])/n

    a = a2**0.5

    print(a)
while True:

    n = int(eval(input()))

    if n == 0:

        break

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

    m = sum(s)/n

    a2 = 0.0

    for i in range(n):

        a2 += (s[i] - m)**2

    a = (a2/n)**0.5

    print(a)
while True:
    n = int(eval(input()))
    if n == 0:
        break
    s = list(map(int, input().split()))
    m = sum(s) / n
    a2 = sum([(s[i] - m) ** 2 for i in range(n)]) / n
    a = a2**0.5
    print(a)

while True:
    n = int(eval(input()))
    if n == 0:
        break
    s = list(map(int, input().split()))
    m = sum(s) / n
    a2 = 0.0
    for i in range(n):
        a2 += (s[i] - m) ** 2
    a = (a2 / n) ** 0.5
    print(a)

-    a2 = sum([(s[i] - m) ** 2 for i in range(n)]) / n -    a = a2**0.5 +    a2 = 0.0 +    for i in range(n): +        a2 += (s[i] - m) ** 2 +    a = (a2 / n) ** 0.5