import java.util.Scanner

object Main {

  def solve(sc: => Scanner): Unit = {
    val N = sc.nextInt
    val A = Array.fill[Int](N)(sc.nextInt)
    val ave = A.sum / N
    println(math.sqrt(A.map(X => (X - ave) * (X - ave)).sum / N))

  }

  def main(args: Array[String]): Unit = {
    val sc: Scanner = new Scanner(System.in)
    solve(sc)
  }
}