import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	} main {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		} scan.hasNext() scan.hasNext scan {
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if(n == 0){
				scan.close();
				break;
			} n == 0 n 0 {
				scan.close();
				break;
			} scan.close() scan.close scan break; int sum = 0; sum 0 int s[] = new int[n]; s new int[n] n for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = scan.nextInt();
				sum += s[i];
			} {
				s[i] = scan.nextInt();
				sum += s[i];
			} s[i] = scan.nextInt() s[i] s i scan.nextInt() scan.nextInt scan sum += s[i] sum s[i] s i double m = Double.valueOf(sum) / Double.valueOf(n); m Double.valueOf(sum) / Double.valueOf(n) Double.valueOf(sum) Double.valueOf Double sum Double.valueOf(n) Double.valueOf Double n double sig = 0; sig 0 for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				sig += Math.pow(s[i] - m, 2);
			} {
				sig += Math.pow(s[i] - m, 2);
			} sig += Math.pow(s[i] - m, 2) sig Math.pow(s[i] - m, 2) Math.pow Math s[i] - m s[i] s i m 2 double a = Math.sqrt(sig / n); a Math.sqrt(sig / n) Math.sqrt Math sig / n sig n System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while(scan.hasNext()){
			int n = scan.nextInt();
			if(n == 0){
				scan.close();
				break;
			}
			int sum = 0;
			int s[] = new int[n];
			for(int i = 0; i < n; i++){
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = Double.valueOf(sum) / Double.valueOf(n);
			double sig = 0;
			for(int i = 0; i < n; i++){
				sig += Math.pow(s[i] - m, 2);
			}
			double a = Math.sqrt(sig / n);
			System.out.println(a);
		}
	}
}