/* ITP1_10_C */
import java.io.*;

class Main
{
  public static int student;
  public static void main(String[] args)
  {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    }
  }
} import java.io.*; io.* java class Main
{
  public static int student;
  public static void main(String[] args)
  {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    }
  }
} Main public static int student; student public static void main(String[] args)
  {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    }
  } main {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    }
  } try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    } catch(Exception e){
      System.out.println(e);
    } Exception e {
      System.out.println(e);
    } System.out.println(e) System.out.println System.out System System.out e {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      } (student = Integer.parseInt(br.readLine())) != 0 (student = Integer.parseInt(br.readLine())) student Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br 0 {
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      } String[] str = br.readLine().split(" "); str br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double[] score = new double[student]; score new double[student] student double mean = 0; mean 0 double variance = 0; variance 0 for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        } int i = 0; int i = 0; i 0 i < student i student i++ i++ i {
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        } {
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        } score[i] = Integer.parseInt(str[i]) score[i] score i Integer.parseInt(str[i]) Integer.parseInt Integer str[i] str i mean += score[i] mean score[i] score i mean /= student mean student for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        } int i = 0; int i = 0; i 0 i < student i student i++ i++ i {
          variance += Math.pow((score[i] - mean), 2);
        } {
          variance += Math.pow((score[i] - mean), 2);
        } variance += Math.pow((score[i] - mean), 2) variance Math.pow((score[i] - mean), 2) Math.pow Math (score[i] - mean) score[i] score i mean 2 variance = variance / student variance variance / student variance student System.out.println(Math.sqrt(variance)) System.out.println System.out System System.out Math.sqrt(variance) Math.sqrt Math variance String[] args args
/* ITP1_10_C */
import java.io.*;

class Main
{
  public static int student;
  public static void main(String[] args)
  {
    try{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      while((student = Integer.parseInt(br.readLine())) != 0){
        String[] str = br.readLine().split(" ");
        double[] score = new double[student];
        double mean = 0;
        double variance = 0;

        for(int i = 0; i < student; i++){
          score[i] = Integer.parseInt(str[i]);
          mean += score[i];
        }
        mean /= student;

        for(int i = 0; i < student; i++){
          variance += Math.pow((score[i] - mean), 2);
        }
        variance = variance / student;
        
        System.out.println(Math.sqrt(variance));
      }
    }catch(Exception e){
      System.out.println(e);
    }
  }
}