
loop do

n = gets.to_i

if n == 0 then
break
end

data = gets.split.map(&:to_f)
m = data.inject(:+)/n.to_f
sum = 0
for i in 1..n
sum += (data[i-1]-m)**2
end

dis = sum/n.to_f
puts Math.sqrt(dis)


end
