import java.io.*;
import java.util.Arrays;
import java.util.Scanner;

public class Main{
	public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	}
} import java.io.*; io.* java import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	}
} Main public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	} main { 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		} true {
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		} String fst = br.readLine(); fst br.readLine() br.readLine br int n = Integer.parseInt(fst); n Integer.parseInt(fst) Integer.parseInt Integer fst if(n==0){break;} n==0 n 0 {break;} break; String line = br.readLine(); line br.readLine() br.readLine br String[] str = line.split(" "); str line.split(" ") line.split line " " double[] s = new double[str.length]; s new double[str.length] str.length str str.length for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			} int j = 0; int j = 0; j 0 j<n j n j++ j++ j {
				s[j] = Double.parseDouble(str[j]);
			} {
				s[j] = Double.parseDouble(str[j]);
			} s[j] = Double.parseDouble(str[j]) s[j] s j Double.parseDouble(str[j]) Double.parseDouble Double str[j] str j double sum = 0.0; sum 0.0 for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			} int j = 0; int j = 0; j 0 j<n j n j++ j++ j {
				sum += s[j];
			} {
				sum += s[j];
			} sum += s[j] sum s[j] s j double num = n; num n double avr = sum/num; avr sum/num sum num double a = 0.0; a 0.0 for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			} int j = 0; int j = 0; j 0 j<n j n j++ j++ j {
				a += (s[j]-avr)*(s[j]-avr);		
			} {
				a += (s[j]-avr)*(s[j]-avr);		
			} a += (s[j]-avr)*(s[j]-avr) a (s[j]-avr)*(s[j]-avr) (s[j]-avr) s[j] s j avr (s[j]-avr) s[j] s j avr a /= num a num a = Math.sqrt(a) a Math.sqrt(a) Math.sqrt Math a System.out.printf("%.6f\n",a) System.out.printf System.out System System.out "%.6f\n" a String[] args args public class Main{
	public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	}
} public class Main{
	public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	}
} Main
import java.io.*;
import java.util.Arrays;
import java.util.Scanner;

public class Main{
	public static void main(String[] args) throws IOException{ 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			String fst = br.readLine();
			int n = Integer.parseInt(fst);
			if(n==0){break;}
			String line = br.readLine();
			String[] str = line.split(" ");
			double[] s = new double[str.length];
			for (int j = 0; j<n ; j++ ) {
				s[j] = Double.parseDouble(str[j]);
			}

			double sum = 0.0;
			for (int j = 0; j<n ; j++ ) {
				sum += s[j];
			}
			double num = n;
			double avr = sum/num;
			double a = 0.0;
			for (int j = 0; j<n ; j++) {
				a += (s[j]-avr)*(s[j]-avr);		
			}
			a /= num;
			a = Math.sqrt(a);
			System.out.printf("%.6f\n",a);
		}
	}
}