import java.io.*;
import java.util.*;
import java.lang.Math;
import java.util.Arrays;

public class Main {
    public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    }
  
} import java.io.*; io.* java import java.util.*; util.* java import java.lang.Math; Math java.lang import java.util.Arrays; Arrays java.util public class Main {
    public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    }
  
} Main public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    } main {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        } true {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        } n = sc.nextInt() n sc.nextInt() sc.nextInt sc if (n == 0)
                break; n == 0 n 0 break; double s[] = new double[n]; s new double[n] n double ave = 0; ave 0 for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                s[i] = sc.nextDouble();
                ave += s[i];
            } {
                s[i] = sc.nextDouble();
                ave += s[i];
            } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc ave += s[i] ave s[i] s i ave /= (double) n ave (double) n double d = 0; d 0 for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                d += (s[i] - ave) * (s[i] - ave);
            } {
                d += (s[i] - ave) * (s[i] - ave);
            } d += (s[i] - ave) * (s[i] - ave) d (s[i] - ave) * (s[i] - ave) (s[i] - ave) s[i] s i ave (s[i] - ave) s[i] s i ave d /= (double) n d (double) n System.out.printf("%.7f\n", Math.sqrt(d)) System.out.printf System.out System System.out "%.7f\n" Math.sqrt(d) Math.sqrt Math d final String[] args args public class Main {
    public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    }
  
} public class Main {
    public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    }
  
} Main
import java.io.*;
import java.util.*;
import java.lang.Math;
import java.util.Arrays;

public class Main {
    public static void main(final String[] args) {

        Scanner sc = new Scanner(System.in);
        
        int n;
        while (true) {
            n = sc.nextInt();
            if (n == 0)
                break;
            double s[] = new double[n];
            double ave = 0;
            for (int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                ave += s[i];
            }

            ave /= (double) n;
            double d = 0;
            for (int i = 0; i < n; i++) {
                d += (s[i] - ave) * (s[i] - ave);
            }
            d /= (double) n;
            System.out.printf("%.7f\n", Math.sqrt(d));
        }
    }
  
}
