loop do
  n = gets.to_i
  break if n == 0

  scores = readline.split.map(&:to_i)
  average = scores.inject(:+).to_f / n
  variance = scores.inject(0.0) {|sum, s| sum += (s - average) ** 2 } / n
  standard_deviation = Math.sqrt(variance)
  p standard_deviation
end