public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
} public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
} Main public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  } run {
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  } java.util.Scanner sc = new java.util.Scanner(in); sc new java.util.Scanner(in) int n; n double[] s; s int i; i double a a ave; ave for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    } ; {
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    } {
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    } n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n == 0)break; n == 0 n 0 break; s = new double[n] s new double[n] n for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      } i = 0; i = 0 i 0 i < n i n i++ i++ i {
        s[i] = sc.nextDouble();
      } {
        s[i] = sc.nextDouble();
      } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc ave = 0.0 ave 0.0 for(i = 0;i < n;i++){
        ave += (double)s[i];
      } i = 0; i = 0 i 0 i < n i n i++ i++ i {
        ave += (double)s[i];
      } {
        ave += (double)s[i];
      } ave += (double)s[i] ave (double)s[i] s i ave /= (double)n ave (double)n a = 0.0 a 0.0 for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      } i = 0; i = 0 i 0 i < n i n i++ i++ i {
        a += (s[i] - ave) * (s[i] - ave);
      } {
        a += (s[i] - ave) * (s[i] - ave);
      } a += (s[i] - ave) * (s[i] - ave) a (s[i] - ave) * (s[i] - ave) (s[i] - ave) s[i] s i ave (s[i] - ave) s[i] s i ave a /= (double)n a (double)n System.out.println(Math.sqrt(a)) System.out.println System.out System System.out Math.sqrt(a) Math.sqrt Math a sc.close() sc.close sc java.io.InputStream in in java.io.PrintStream out out public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  } main {
    (new Main()).run(System.in, System.out);
  } (new Main()).run(System.in, System.out) (new Main()).run (new Main()) System.in System System.in System.out System System.out String[] args args public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
} public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
} Main
public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int n;
    double[] s;
    int i;
    double a, ave;

    for(;;){
      n = sc.nextInt();
      if(n == 0)break;
      s = new double[n];
      for(i = 0;i < n;i++){
        s[i] = sc.nextDouble();
      }

      ave = 0.0;
      for(i = 0;i < n;i++){
        ave += (double)s[i];
      }
      ave /= (double)n;

      a = 0.0;
      for(i = 0;i < n;i++){
        a += (s[i] - ave) * (s[i] - ave);
      }
      a /= (double)n;
      System.out.println(Math.sqrt(a));
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
}