#!/usr/bin/env ruby

result = []
while true do
    number = gets.to_i
    if number == 0 then
        break
    end
    points = gets.split.map(&:to_f)
    nijou = 0;ave = 0
    variance = 0

    points.each do |p|
        nijou +=  p ** 2
        ave += p
    end

    ave = (ave / number) ** 2
    nijou = nijou / number

    variance = nijou - ave
    standard_deviation = (variance) ** 0.5
    result << standard_deviation
end
puts result
