import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class Main{
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}
 import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.IOException; IOException java.io public class Main{
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
} Main public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    } main {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        } catch(IOException e) {
            e.printStackTrace();
        } IOException e {
            e.printStackTrace();
        } e.printStackTrace() e.printStackTrace e {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            } true {
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            } int x = Integer.parseInt(br.readLine()); x Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if(x==0){
                    break;
                } x==0 x 0 {
                    break;
                } break; String[] arr = br.readLine().split("\\s"); arr br.readLine().split("\\s") br.readLine().split br.readLine() br.readLine br "\\s" Double[] data = new Double[x]; data new Double[x] x Double sum = 0.0; sum 0.0 for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                } int i=0; int i=0; i 0 i<x i x i++ i++ i {
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                } {
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                } data[i] = Double.parseDouble(arr[i]) data[i] data i Double.parseDouble(arr[i]) Double.parseDouble Double arr[i] arr i sum += data[i] sum data[i] data i Double avg = sum/x; avg sum/x sum x Double tmp = 0.0; tmp 0.0 for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                } int i=0; int i=0; i 0 i<x i x i++ i++ i {
                    tmp += Math.pow(data[i] - avg, 2);
                } {
                    tmp += Math.pow(data[i] - avg, 2);
                } tmp += Math.pow(data[i] - avg, 2) tmp Math.pow(data[i] - avg, 2) Math.pow Math data[i] - avg data[i] data i avg 2 Double stdev = Math.sqrt(tmp/x); stdev Math.sqrt(tmp/x) Math.sqrt Math tmp/x tmp x System.out.println(String.valueOf(stdev)) System.out.println System.out System System.out String.valueOf(stdev) String.valueOf String stdev String[] args args public class Main{
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
} public class Main{
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class Main{
    public static void main(String[] args) {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try {
            while(true){
                int x = Integer.parseInt(br.readLine());
                if(x==0){
                    break;
                }
                
                String[] arr = br.readLine().split("\\s");
                Double[] data = new Double[x];
                Double sum = 0.0;
                for(int i=0; i<x; i++){
                    data[i] = Double.parseDouble(arr[i]);
                    sum += data[i];
                }
                
                Double avg = sum/x;
                Double tmp = 0.0;
                for(int i=0; i<x; i++){
                    tmp += Math.pow(data[i] - avg, 2);
                }
                Double stdev = Math.sqrt(tmp/x);
                System.out.println(String.valueOf(stdev));
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}

