import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	}
} Main public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	} main {
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	} Scanner std = new Scanner(System.in); std new Scanner(System.in) while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		} true {
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		} int n = Integer.parseInt(std.next()); n Integer.parseInt(std.next()) Integer.parseInt Integer std.next() std.next std if(n==0){break;} n==0 n 0 {break;} break; double score[] = new double[n]; score new double[n] n double ave = 0; ave 0 for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			} {
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			} score[i] = Double.parseDouble(std.next()) score[i] score i Double.parseDouble(std.next()) Double.parseDouble Double std.next() std.next std ave += score[i] ave score[i] score i ave /= n ave n double sd = 0; sd 0 for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sd += Math.pow((score[i]-ave),2);
			} {
				sd += Math.pow((score[i]-ave),2);
			} sd += Math.pow((score[i]-ave),2) sd Math.pow((score[i]-ave),2) Math.pow Math (score[i]-ave) score[i] score i ave 2 sd /= n sd n sd = Math.pow(sd, 0.5) sd Math.pow(sd, 0.5) Math.pow Math sd 0.5 System.out.println(String.format("%.5f", sd)) System.out.println System.out System System.out String.format("%.5f", sd) String.format String "%.5f" sd String[] args args public class Main {
	public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	}
} public class Main {
	public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner std = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(std.next());
			if(n==0){break;}

			double score[] = new double[n];
			double ave = 0;
			for(int i=0; i<n; i++){
				score[i] = Double.parseDouble(std.next());
				ave += score[i];
			}
			ave /= n;
			double sd = 0;
			for(int i=0; i<n; i++){
				sd += Math.pow((score[i]-ave),2);
			}
			sd /= n;
			sd = Math.pow(sd, 0.5);

			System.out.println(String.format("%.5f", sd));
		}
	}
}