import java.util.*;
import java.text.*;
/*
Main class for AOJ where there is no input.
*/
public class Main{
   public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main
   
   
}//class import java.util.*; util.* java import java.text.*; text.* java public class Main{
   public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main
   
   
}//class Main public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main main {
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String[] arr; arr int n; n int[] score; score double avg; avg int sum; sum double stdDeviation; stdDeviation while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      } true {
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      } n = Integer.parseInt(sc.nextLine()) n Integer.parseInt(sc.nextLine()) Integer.parseInt Integer sc.nextLine() sc.nextLine sc if(n == 0){
            break;
         } n == 0 n 0 {
            break;
         } break; sum = 0 sum 0 stdDeviation = 0 stdDeviation 0 arr = sc.nextLine().split(" ") arr sc.nextLine().split(" ") sc.nextLine().split sc.nextLine() sc.nextLine sc " " score = new int[arr.length] score new int[arr.length] arr.length arr arr.length for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         } int i = 0; int i = 0; i 0 i < n i n i ++ i ++ i {
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         } {
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         } score[i] = Integer.parseInt(arr[i]) score[i] score i Integer.parseInt(arr[i]) Integer.parseInt Integer arr[i] arr i sum += score[i] sum score[i] score i avg = sum/(double)n avg sum/(double)n sum (double)n for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         } int i = 0; int i = 0; i 0 i < n i n i ++ i ++ i {
            stdDeviation += Math.pow((double)score[i] - avg,2);
         } {
            stdDeviation += Math.pow((double)score[i] - avg,2);
         } stdDeviation += Math.pow((double)score[i] - avg,2) stdDeviation Math.pow((double)score[i] - avg,2) Math.pow Math (double)score[i] - avg (double)score[i] score i avg 2 stdDeviation /= (double)n stdDeviation (double)n stdDeviation = Math.sqrt(stdDeviation) stdDeviation Math.sqrt(stdDeviation) Math.sqrt Math stdDeviation System.out.println(String.format("%.6f",stdDeviation)) System.out.println System.out System System.out String.format("%.6f",stdDeviation) String.format String "%.6f" stdDeviation String[] args args public class Main{
   public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main
   
   
}//class public class Main{
   public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main
   
   
}//class Main
import java.util.*;
import java.text.*;
/*
Main class for AOJ where there is no input.
*/
public class Main{
   public static void main(String[] args){
      Scanner sc = new Scanner(System.in);
      String[] arr;
      int n;
      int[] score;
      double avg;
      int sum;
      double stdDeviation;
      
      while(true){
         n = Integer.parseInt(sc.nextLine());
         if(n == 0){
            break;
         }
         
         sum = 0;
         stdDeviation = 0;
         
         arr = sc.nextLine().split(" ");
         score = new int[arr.length];
         
         for(int i = 0; i < n; i ++){
            score[i] = Integer.parseInt(arr[i]);
            sum += score[i];
         }
         
         avg = sum/(double)n;
         
         for(int i = 0; i < n; i ++){
            stdDeviation += Math.pow((double)score[i] - avg,2);
         }
         stdDeviation /= (double)n;
         stdDeviation = Math.sqrt(stdDeviation);
         
         System.out.println(String.format("%.6f",stdDeviation));
      }
   }//main
   
   
}//class