# encoding: utf-8                                                                      

def main
  while n = gets.chomp.to_i and n != 0
    nums = gets.chomp.split(/\s/).collect { |x| x.to_f}
    avg = nums.inject(0) { |s, e| s + e} / nums.size
    ans = 0.0
    nums.each do |num|
      ans += (num - avg) ** 2
    end
    puts ("%.6f" %  Math.sqrt((ans / nums.size)))
  end
end

main