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