import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Main {
	public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	}
} Main public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	} main {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		} true {
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		} int n=Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if(n==0)break; n==0 n 0 break; String[] dat=br.readLine().split(" "); dat br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int[] p= new int[n]; p new int[n] n int sum=0; sum 0 double h h hsa; hsa for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			} {
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			} p[i] = Integer.parseInt(dat[i]) p[i] p i Integer.parseInt(dat[i]) Integer.parseInt Integer dat[i] dat i sum +=p[i] sum p[i] p i h=(double)sum/n h (double)sum/n (double)sum n double bun=0; bun 0 for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				bun +=(p[i]-h)*(p[i]-h);
			} {
				bun +=(p[i]-h)*(p[i]-h);
			} bun +=(p[i]-h)*(p[i]-h) bun (p[i]-h)*(p[i]-h) (p[i]-h) p[i] p i h (p[i]-h) p[i] p i h hsa=(double)Math.sqrt(bun/n) hsa (double)Math.sqrt(bun/n) Math.sqrt Math bun/n bun n System.out.printf("%.8f\n",hsa) System.out.printf System.out System System.out "%.8f\n" hsa String[] args args public class Main {
	public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	}
} public class Main {
	public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Main {
	public static void main(String[] args)throws IOException {

		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n=Integer.parseInt(br.readLine());
			if(n==0)break;
			String[] dat=br.readLine().split(" ");
			int[] p= new int[n];
			int sum=0;
			double h,hsa;
			for (int i=0;i<n;i++){
				p[i] = Integer.parseInt(dat[i]);
				sum +=p[i];
			}
			
			h=(double)sum/n;
			double bun=0;
			for (int i=0;i<n;i++){
				bun +=(p[i]-h)*(p[i]-h);
			}
			hsa=(double)Math.sqrt(bun/n);	
			System.out.printf("%.8f\n",hsa);
		}
	}
}