import java.util.Scanner;

class Main {  
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    
    while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    }
  }
} import java.util.Scanner; Scanner java.util class Main {  
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    
    while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    }
  }
} Main public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    
    while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    }
  } main {
    Scanner in = new Scanner(System.in);
    
    while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    }
  } Scanner in = new Scanner(System.in); in new Scanner(System.in) while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    } in.hasNext() in.hasNext in {
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    } int n = in.nextInt(); n in.nextInt() in.nextInt in if (n == 0) break; n == 0 n 0 break; int[] numbers = new int[n]; numbers new int[n] n long double_sum = 0; double_sum 0 long sum_double = 0; sum_double 0 for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      } {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      } numbers[i] = in.nextInt() numbers[i] numbers i in.nextInt() in.nextInt in double_sum += numbers[i] double_sum numbers[i] numbers i double_sum = double_sum * double_sum double_sum double_sum * double_sum double_sum double_sum for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]); int i = 0; int i = 0; i 0 i < n i n i++ i++ i sum_double += (numbers[i] * numbers[i]); sum_double += (numbers[i] * numbers[i]) sum_double (numbers[i] * numbers[i]) numbers[i] numbers i numbers[i] numbers i double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n); sd Math.sqrt((sum_double - double_sum / (double)n) / (double)n) Math.sqrt Math (sum_double - double_sum / (double)n) / (double)n (sum_double - double_sum / (double)n) sum_double double_sum / (double)n double_sum (double)n (double)n System.out.printf("%5.8f", sd) System.out.printf System.out System System.out "%5.8f" sd System.out.println() System.out.println System.out System System.out String[] args args
import java.util.Scanner;

class Main {  
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    
    while (in.hasNext()){
      int n = in.nextInt();
      if (n == 0) break;
      int[] numbers = new int[n];
      long double_sum = 0;
      long sum_double = 0;
      
      for (int i = 0; i < n; i++) {
        numbers[i] = in.nextInt();
        double_sum += numbers[i];
      }
      double_sum = double_sum * double_sum;
      for (int i = 0; i < n; i++) sum_double += (numbers[i] * numbers[i]);
      
      double sd = Math.sqrt((sum_double - double_sum / (double)n) / (double)n);
      
      System.out.printf("%5.8f", sd);
      System.out.println();
    }
  }
}