import java.util.Scanner;

public class Main {
	private static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		while(true){
			int n = sc.nextInt();
			
			if(n == 0){
				break;
			}
			
			double[] s = new double[n];
			double sum = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				sum += s[i];
			}
			
			double ave = sum / n;
			double psum = 0;
			for(int i=0; i<n; i++){
				psum += Math.pow(s[i] - ave, 2);
			}
			
			double std = Math.sqrt(psum / n);
			System.out.println(std);
			
		}
	}

} import java.util.Scanner; Scanner java.util public class Main {
	private static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		while(true){
			int n = sc.nextInt();
			
			if(n == 0){
				break;
			}
			
			double[] s = new double[n];
			double sum = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				sum += s[i];
			}
			
			double ave = sum / n;
			double psum = 0;
			for(int i=0; i<n; i++){
				psum += Math.pow(s[i] - ave, 2);
			}
			
			double std = Math.sqrt(psum / n);
			System.out.println(std);
			
		}
	}

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

	public static void main(String[] args) {
		while(true){
			int n = sc.nextInt();
			
			if(n == 0){
				break;
			}
			
			double[] s = new double[n];
			double sum = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				sum += s[i];
			}
			
			double ave = sum / n;
			double psum = 0;
			for(int i=0; i<n; i++){
				psum += Math.pow(s[i] - ave, 2);
			}
			
			double std = Math.sqrt(psum / n);
			System.out.println(std);
			
		}
	}

} public class Main {
	private static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		while(true){
			int n = sc.nextInt();
			
			if(n == 0){
				break;
			}
			
			double[] s = new double[n];
			double sum = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				sum += s[i];
			}
			
			double ave = sum / n;
			double psum = 0;
			for(int i=0; i<n; i++){
				psum += Math.pow(s[i] - ave, 2);
			}
			
			double std = Math.sqrt(psum / n);
			System.out.println(std);
			
		}
	}

} Main
import java.util.Scanner;

public class Main {
	private static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		while(true){
			int n = sc.nextInt();
			
			if(n == 0){
				break;
			}
			
			double[] s = new double[n];
			double sum = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextDouble();
				sum += s[i];
			}
			
			double ave = sum / n;
			double psum = 0;
			for(int i=0; i<n; i++){
				psum += Math.pow(s[i] - ave, 2);
			}
			
			double std = Math.sqrt(psum / n);
			System.out.println(std);
			
		}
	}

}