import java.io.*;

class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		}
	}
} import java.io.*; io.* java class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		}
	}
} Main public static void main(String[] args) throws Exception {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		}
	} main {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		}
	} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) int n=Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		} n!=0 n 0 {
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		} double[] s=new double[n]; s new double[n] n String[] a=br.readLine().split(" "); a br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double sum=0; sum 0 for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			} {
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			} s[i]=Double.parseDouble(a[i]) s[i] s i Double.parseDouble(a[i]) Double.parseDouble Double a[i] a i sum+=s[i] sum s[i] s i double m=sum/n; m sum/n sum n double v=0; v 0 for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				v+=Math.pow(s[i]-m, 2);
			} {
				v+=Math.pow(s[i]-m, 2);
			} v+=Math.pow(s[i]-m, 2) v Math.pow(s[i]-m, 2) Math.pow Math s[i]-m s[i] s i m 2 System.out.printf("%.8f%n", Math.sqrt(v/n)) System.out.printf System.out System System.out "%.8f%n" Math.sqrt(v/n) Math.sqrt Math v/n v n n=Integer.parseInt(br.readLine()) n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br String[] args args
import java.io.*;

class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		while(n!=0){
			double[] s=new double[n];
			String[] a=br.readLine().split(" ");
			double sum=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(a[i]);
				sum+=s[i];
			}
			double m=sum/n;
			double v=0;
			for(int i=0;i<n;i++){
				v+=Math.pow(s[i]-m, 2);
			}
	        System.out.printf("%.8f%n", Math.sqrt(v/n));
	        n=Integer.parseInt(br.readLine());
		}
	}
}