import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	} main {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		} ; {
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		} {
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0)break; n==0 n 0 break; double st = 0; st 0 double m = 0; m 0 double to = 0; to 0 double a = 0; a 0 double[] s = new double[n]; s new double[n] n for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i] = sc.nextDouble();
				st += s[i];
			} {
				s[i] = sc.nextDouble();
				st += s[i];
			} s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc st += s[i] st s[i] s i m = st/n m st/n st n for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				to += Math.pow(s[i]-m, 2);
			} {
				to += Math.pow(s[i]-m, 2);
			} to += Math.pow(s[i]-m, 2) to Math.pow(s[i]-m, 2) Math.pow Math s[i]-m s[i] s i m 2 a = Math.sqrt(to/n) a Math.sqrt(to/n) Math.sqrt Math to/n to 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 sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for(;;){
			int n = sc.nextInt();
			if(n==0)break;
			
			double st = 0;
			double m = 0;
			double to = 0;
			double a = 0;
			double[] s = new double[n];
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				st += s[i];
			}
			m = st/n;
			for(int i=0; i<n; i++){
				to += Math.pow(s[i]-m, 2);
			}
			a = Math.sqrt(to/n);
			System.out.println(a);
		}
	}
}