import scala.math._

object Main extends App {
  val scanner = new java.util.Scanner(System.in)

  val inputs = Iterator.continually {
    val n = scanner.nextInt()
    val sn = (1 to n).map { _ =>
      scanner.nextInt()
    }

    (n, sn)
  }.takeWhile(_._1 != 0)

  val outputs = inputs.map {
    case (n, sn) =>
      val m = sn.sum / n
      val alpha2 = sn.foldLeft(0.0) { (acc, s) =>
        acc + pow(s - m, 2) / n
      }
      sqrt(alpha2)
  }

  outputs.foreach(println)
}