import java.util.*;
import java.io.*;

public class Main {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	}
}
 import java.util.*; util.* java import java.io.*; io.* java public class Main {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	}
} Main public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	} main {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	} Scanner in=new Scanner(System.in); in new Scanner(System.in) PrintWriter out=new PrintWriter(System.out); out new PrintWriter(System.out) while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		} true {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		} int n=in.nextInt(); n in.nextInt() in.nextInt in if(n==0)break; n==0 n 0 break; double s[]=new double[n] s new double[n] n ave=0; ave 0 for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			} {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			} s[i]=Integer.parseInt(in.next()) s[i] s i Integer.parseInt(in.next()) Integer.parseInt Integer in.next() in.next in ave+=s[i] ave s[i] s i ave/=n ave n double dev=0; dev 0 for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2); int i=0; int i=0; i 0 i<n i n i++ i++ i dev+=Math.pow(s[i]-ave, 2); dev+=Math.pow(s[i]-ave, 2) dev Math.pow(s[i]-ave, 2) Math.pow Math s[i]-ave s[i] s i ave 2 dev=Math.sqrt(dev/n) dev Math.sqrt(dev/n) Math.sqrt Math dev/n dev n out.printf("%f\n",dev) out.printf out "%f\n" dev out.flush() out.flush out String[] args args public class Main {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	}
} public class Main {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	}
} Main
import java.util.*;
import java.io.*;

public class Main {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		PrintWriter out=new PrintWriter(System.out);
		while(true) {
			int n=in.nextInt();
			if(n==0)break;
			double s[]=new double[n], ave=0;
			
			for(int i=0;i<n;i++) {
				s[i]=Integer.parseInt(in.next());
				ave+=s[i];
			}
			ave/=n;
			double dev=0;
			for(int i=0;i<n;i++)dev+=Math.pow(s[i]-ave, 2);
			dev=Math.sqrt(dev/n);
			out.printf("%f\n",dev);
		}
		out.flush();
	}
}

