data=[]
ans=[]
while
    n=gets.to_f
    if n==0 then break end
    data << [n, gets.split.map(&:to_i)]
end
data.each do |e|
    n,s=e
    m=s.inject{|a,b|a+b}/n
    bunsan=s.map{|num|(num-m)**2}.inject{|a,b|a+b}/n
    ans << Math.sqrt(bunsan)
end
ans.each{|a|p a}
