object Main extends App {
  val sc = new java.util.Scanner(System.in)
  while (sc.hasNext) {
    val n = sc.nextInt()
    if (n == 0) sys.exit()
    val scores = List.fill(n)(sc.nextInt())
    println(f"${calc(n, scores).toDouble}%.8f")
  }

  def calc(n: Int, scores: List[Int]): BigDecimal = {
    val m = (scores.sum.toDouble / n).toBigDecimal
    val dispersion = ((scores.map(e => (e - m).squared).sum) / n)
    dispersion.sqRoot.abs
  }

  implicit class DoubleExtends(val d: Double) extends AnyVal {
    def toBigDecimal = BigDecimal(d)
  }

  implicit class BigDecimalExtends(val b: BigDecimal) extends AnyVal {

    import scala.math.sqrt

    def squared = b * b

    def sqRoot = sqrt(b.toDouble).toBigDecimal
  }

}