while true
  n = gets.split.map(&:to_i)
break if n == 0

 n.times do
 s = gets.split.map(|s| s.to_f)
 end 
 
 mean = s.sum / n
 sum_of_squares = samples.inject(0){|sum, i| sum + (i - mean) ** 2 }
 s2 = sum_of_squares / n
 s = Math.sqrt(s2)
 
 puts s
end 
