object Main extends App {
  val sc = new java.util.Scanner(Console.in)

  def next() = sc.next
  def nextInt() = Integer.parseInt(next)
  def nextDouble() = java.lang.Double.parseDouble(next)

  def solve(n: Int): Unit = {
    if (n > 0) {
      val xs = List.fill(n)(nextDouble)
      val m = xs.sum / n
      val aa = xs.fold(0.0) { (z, e) => z + (e - m) * (e - m) } / n
      println(math.sqrt(aa))
      solve(nextInt)
    }
  }

  solve(nextInt)
}

