while true
  n = gets.to_f
break if n == 0

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