until (n = gets.strip.to_i) == 0
	points = gets.strip.split(" ").map {|i| i.to_f}
	avg = (points.reduce(0.0){|sum, p| sum += p}) / n.to_f
	var = points.reduce(0.0){|sum, p| sum += (p - avg) ** 2} / n.to_f
	std = var ** 0.5
	puts std.floor(4)
end
