import statistics as st

while True:

    n = int(eval(input()))

    if n == 0:

        break

    x = tuple(map(float, input().strip().split()))

    y = st.mean(x)**2

    z = st.mean(list(map(pow, x, (2 for i in range(n)))))

    print(((z-y)**0.5))
while True:

    n = int(eval(input()))

    if n == 0:

        break

    x = tuple(map(float, input().strip().split()))

    y = (sum(x)/n)**2

    z = sum(map(pow, x, (2 for i in range(n))))/n

    print(((z-y)**0.5))
import statistics as st

while True:
    n = int(eval(input()))
    if n == 0:
        break
    x = tuple(map(float, input().strip().split()))
    y = st.mean(x) ** 2
    z = st.mean(list(map(pow, x, (2 for i in range(n)))))
    print(((z - y) ** 0.5))

while True:
    n = int(eval(input()))
    if n == 0:
        break
    x = tuple(map(float, input().strip().split()))
    y = (sum(x) / n) ** 2
    z = sum(map(pow, x, (2 for i in range(n)))) / n
    print(((z - y) ** 0.5))

-import statistics as st - -    y = st.mean(x) ** 2 -    z = st.mean(list(map(pow, x, (2 for i in range(n))))) +    y = (sum(x) / n) ** 2 +    z = sum(map(pow, x, (2 for i in range(n)))) / n