
import java.util.Scanner;

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

import java.util.Scanner;

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