import scala.math.sqrt
import scala.io.Source

object Main extends App {
  val src: Iterator[String] = Source.stdin.getLines

  def deviator(n: Double, li: List[Double]): Double = {
    def predicate(a: Double, b: Double): Double = {
      val avg = li.sum / n
      a + (b-avg)*(b-avg)
    }

    sqrt(li.foldLeft(0.0)(predicate) / n)
  }

  for (n <- src if src.hasNext) {
    val li = src.next.split(" ").map(_.toDouble).toList
    println(deviator(n.toDouble, li))
  }
}