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