import java.io.*;
import java.util.*;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	}

} import java.io.*; io.* java import java.util.*; util.* java public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	}

} Main /**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	} main {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	} Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in))); s new Scanner(new BufferedReader(new InputStreamReader(System.in))) while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		} s.hasNext() s.hasNext s {
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		} Integer student_num = Integer.parseInt(s.next()); student_num Integer.parseInt(s.next()) Integer.parseInt Integer s.next() s.next s if(student_num == 0){
				break;
			} student_num == 0 student_num 0 {
				break;
			} break; ArrayList<Integer> score_list = new ArrayList<Integer>(); score_list new ArrayList<Integer>() for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			} int i = 0; int i = 0; i 0 i < student_num i student_num i++ i++ i {
				score_list.add(Integer.parseInt(s.next()));
			} {
				score_list.add(Integer.parseInt(s.next()));
			} score_list.add(Integer.parseInt(s.next())) score_list.add score_list Integer.parseInt(s.next()) Integer.parseInt Integer s.next() s.next s Integer total = 0; total 0 for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			} int i = 0; int i = 0; i 0 i < student_num i student_num i++ i++ i {
				total += score_list.get(i);
			} {
				total += score_list.get(i);
			} total += score_list.get(i) total score_list.get(i) score_list.get score_list i double m = (double)total / student_num; m (double)total / student_num (double)total student_num double dev = 0; dev 0 for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			} int i = 0; int i = 0; i 0 i < student_num i student_num i++ i++ i {
				dev += Math.pow(score_list.get(i) - m, 2);
			} {
				dev += Math.pow(score_list.get(i) - m, 2);
			} dev += Math.pow(score_list.get(i) - m, 2) dev Math.pow(score_list.get(i) - m, 2) Math.pow Math score_list.get(i) - m score_list.get(i) score_list.get score_list i m 2 double standard_dev = Math.sqrt(dev / student_num); standard_dev Math.sqrt(dev / student_num) Math.sqrt Math dev / student_num dev student_num System.out.println(String.format("%.8f", standard_dev)) System.out.println System.out System System.out String.format("%.8f", standard_dev) String.format String "%.8f" standard_dev String[] args args public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	}

} public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	}

} Main
import java.io.*;
import java.util.*;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		while(s.hasNext()){
			Integer student_num = Integer.parseInt(s.next());
			if(student_num == 0){
				break;
			}

			ArrayList<Integer> score_list = new ArrayList<Integer>();
			for(int i = 0; i < student_num; i++){
				score_list.add(Integer.parseInt(s.next()));
			}
			Integer total = 0;
			for(int i = 0; i < student_num; i++){
				total += score_list.get(i);
			}
			double m = (double)total / student_num;
			double dev = 0;
			for(int i = 0; i < student_num; i++){
				dev += Math.pow(score_list.get(i) - m, 2);
			}
			double standard_dev = Math.sqrt(dev / student_num);
			System.out.println(String.format("%.8f", standard_dev));
		}

	}

}