import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.text.DecimalFormat;

public class Main {

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    }


}
 import java.io.BufferedReader; BufferedReader java.io import java.io.BufferedWriter; BufferedWriter java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.OutputStreamWriter; OutputStreamWriter java.io import java.io.IOException; IOException java.io import java.text.DecimalFormat; DecimalFormat java.text public class Main {

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    }


} Main public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    } main {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); bw new BufferedWriter(new OutputStreamWriter(System.out)) DecimalFormat df = new DecimalFormat("0.00000000"); df new DecimalFormat("0.00000000") String input; input while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        } !(input = br.readLine()).equals("0") (input = br.readLine()).equals("0") (input = br.readLine()).equals (input = br.readLine()) input br.readLine() br.readLine br "0" {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        } int n = Integer.parseInt(input); n Integer.parseInt(input) Integer.parseInt Integer input String[] st = br.readLine().split(" "); st br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double sum = 0; sum 0 double[] s = new double[n]; s new double[n] n for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                sum += s[i] = Double.parseDouble(st[i]);
            } {
                sum += s[i] = Double.parseDouble(st[i]);
            } sum += s[i] = Double.parseDouble(st[i]) sum s[i] = Double.parseDouble(st[i]) s[i] s i Double.parseDouble(st[i]) Double.parseDouble Double st[i] st i double m = sum / (double) n; m sum / (double) n sum (double) n double result = 0; result 0 for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                result += Math.pow(s[i] - m, 2);
            } {
                result += Math.pow(s[i] - m, 2);
            } result += Math.pow(s[i] - m, 2) result Math.pow(s[i] - m, 2) Math.pow Math s[i] - m s[i] s i m 2 bw.append(df.format(Math.sqrt(result / (double) n)) + "\n") bw.append bw df.format(Math.sqrt(result / (double) n)) + "\n" df.format(Math.sqrt(result / (double) n)) df.format df Math.sqrt(result / (double) n) Math.sqrt Math result / (double) n result (double) n "\n" bw.flush() bw.flush bw String args[] args public class Main {

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    }


} public class Main {

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    }


} Main
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.text.DecimalFormat;

public class Main {

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        DecimalFormat df = new DecimalFormat("0.00000000");
        String input;
        while (!(input = br.readLine()).equals("0")) {
            int n = Integer.parseInt(input);
            String[] st = br.readLine().split(" ");
            double sum = 0;
            double[] s = new double[n];
            for (int i = 0; i < n; i++) {
                sum += s[i] = Double.parseDouble(st[i]);
            }
            double m = sum / (double) n;
            double result = 0;
            for (int i = 0; i < n; i++) {
                result += Math.pow(s[i] - m, 2);
            }
            bw.append(df.format(Math.sqrt(result / (double) n)) + "\n");
        }
        bw.flush();
    }


}

