import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} 

} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} 

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} main {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		} true {
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0) break; n == 0 n 0 break; double[] score = new double[n]; score new double[n] n double sum = 0.0; sum 0.0 for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				score[i] = sc.nextDouble();
				sum += score[i];
			} {
				score[i] = sc.nextDouble();
				sum += score[i];
			} score[i] = sc.nextDouble() score[i] score i sc.nextDouble() sc.nextDouble sc sum += score[i] sum score[i] score i double m = sum / n; m sum / n sum n sum = 0.0 sum 0.0 for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			} int j = 0; int j = 0; j 0 j < n j n j++ j++ j {
				sum += Math.pow((score[j] - m), 2);
			} {
				sum += Math.pow((score[j] - m), 2);
			} sum += Math.pow((score[j] - m), 2) sum Math.pow((score[j] - m), 2) Math.pow Math (score[j] - m) score[j] score j m 2 System.out.printf("%.8f\n", Math.sqrt(sum / n)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(sum / n) Math.sqrt Math sum / n sum n String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} 

} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} 

} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			double[] score = new double[n];
			double sum = 0.0;

			for(int i = 0; i < n; i++){
				score[i] = sc.nextDouble();
				sum += score[i];
			}
			double m = sum / n;
			sum = 0.0;
			for(int j = 0; j < n; j++){
				sum += Math.pow((score[j] - m), 2);
			}
			System.out.printf("%.8f\n", Math.sqrt(sum / n));
		}
	} 

}
