

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 ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	}
} 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 ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	}
} Main public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	} main {
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	} BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) ); br new BufferedReader( new InputStreamReader( System.in ) ) int i; i String n; n double avg avg a a sum1 sum1 sum2; sum2 while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		} true {
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		} sum1=0 sum1 0 sum2=0 sum2 0 a=0 a 0 n=br.readLine() n br.readLine() br.readLine br if(n.equals("0"))break; n.equals("0") n.equals n "0" break; int num=Integer.parseInt(n); num Integer.parseInt(n) Integer.parseInt Integer n String c=br.readLine(); c br.readLine() br.readLine br String b[]=c.split(" "); b c.split(" ") c.split c " " double d=0 d 0 sum=0; sum 0 double e[]=new double[num]; e new double[num] num for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			} i=0; i=0 i 0 i<num i num i++ i++ i {

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			} {

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			} e[i] = Double.parseDouble( b[i] ) e[i] e i Double.parseDouble( b[i] ) Double.parseDouble Double b[i] b i sum1+=e[i] sum1 e[i] e i avg=sum1/num avg sum1/num sum1 num for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			} i=0; i=0 i 0 i<num i num i++ i++ i {

				sum2+= (Math.pow((e[i]-avg),2)/num);
			} {

				sum2+= (Math.pow((e[i]-avg),2)/num);
			} sum2+= (Math.pow((e[i]-avg),2)/num) sum2 (Math.pow((e[i]-avg),2)/num) Math.pow((e[i]-avg),2) Math.pow Math (e[i]-avg) e[i] e i avg 2 num a=Math.sqrt(sum2) a Math.sqrt(sum2) Math.sqrt Math sum2 System.out.printf(a + "\n" ) System.out.printf System.out System System.out a + "\n" a "\n" String[] args args public class Main {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	}
} public class Main {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	}
} 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 ) );

		int i;
		String n;
		double avg,a,sum1,sum2;
		//double[] x = new double[1000 + 1];

		while(true){
			sum1=0;
			sum2=0;
			a=0;
			n=br.readLine();
			if(n.equals("0"))break;
			int num=Integer.parseInt(n);

			String c=br.readLine();
			String b[]=c.split(" ");
			double d=0,sum=0;
			double e[]=new double[num];

			for(i=0;i<num;i++){

				e[i] = Double.parseDouble( b[i] );

				sum1+=e[i];
			}
			avg=sum1/num;
			for(i=0;i<num;i++){

				sum2+= (Math.pow((e[i]-avg),2)/num);
			}
			a=Math.sqrt(sum2);
			System.out.printf(a + "\n" );
		}

	}
}