import static java.lang.Math.*;

import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	}
	public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	}
} import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	}
	public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	}
} Main public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	} main {
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	} Scanner scan = null; scan null try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		} {
			if(scan!=null)scan.close();
		} if(scan!=null)scan.close(); scan!=null scan null scan.close() scan.close scan {
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		} scan = new Scanner(System.in) scan new Scanner(System.in) while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			} true {
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if(n == 0)break; n == 0 n 0 break; int[] data = new int[n]; data new int[n] n for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				} int i = 0 ; int i = 0 ; i 0 i < data.length i data.length data data.length i++ i++ i {
					data[i] = scan.nextInt();
				} {
					data[i] = scan.nextInt();
				} data[i] = scan.nextInt() data[i] data i scan.nextInt() scan.nextInt scan double ave = ave(data); ave ave(data) ave data double alpha = 0; alpha 0 for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				} int i = 0 ; int i = 0 ; i 0 i < n i n i++ i++ i {
					alpha += pow((data[i] - ave),2) / n;
				} {
					alpha += pow((data[i] - ave),2) / n;
				} alpha += pow((data[i] - ave),2) / n alpha pow((data[i] - ave),2) / n pow((data[i] - ave),2) pow (data[i] - ave) data[i] data i ave 2 n alpha =Math.sqrt(alpha) alpha Math.sqrt(alpha) Math.sqrt Math alpha System.out.println(alpha) System.out.println System.out System System.out alpha String[] args args public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	} ave {
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	} double sum = 0; sum 0 for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		} int i = 0 ; int i = 0 ; i 0 i < data.length i data.length data data.length i++ i++ i {
			sum += data[i];
		} {
			sum += data[i];
		} sum += data[i] sum data[i] data i return sum / data.length; sum / data.length sum data.length data data.length int [] data data public class Main{
	public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	}
	public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	}
} public class Main{
	public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	}
	public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	}
} Main
import static java.lang.Math.*;

import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner scan = null;
		try{
			scan = new Scanner(System.in);
			while(true){
				int n = scan.nextInt();
				if(n == 0)break;
				int[] data = new int[n];
				for(int i = 0 ; i < data.length;i++){
					data[i] = scan.nextInt();
				}
				double ave = ave(data);
				double alpha = 0;
				for(int i = 0 ; i < n;i++){
					alpha += pow((data[i] - ave),2) / n;
				}
				alpha =Math.sqrt(alpha);
				System.out.println(alpha);
			}
		}finally{
			if(scan!=null)scan.close();
		}
	}
	public static double ave (int [] data){
		double sum = 0;
		for(int i = 0 ; i < data.length;i++){
			sum += data[i];
		}
		return sum / data.length;
	}
}