res=Array.new
loop do
n=gets.to_i
if n==0 then break end
d=gets.split(' ').map(&:to_f)
m=d.inject(0.00000){|r,i|r+=i}/d.size
s=0
d.each do |x|
  s+=(x-m)*(x-m)
end
res.push(Math.sqrt(s/n))
end

res.each do |r|
    printf("%f\n",r)
end