import java.util.Scanner;
import java.lang.Math;


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

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    }
} import java.util.Scanner; Scanner java.util import java.lang.Math; Math java.lang public class Main {
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    }
} Main public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    } main {

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n; n double[] ans = new double[1000]; ans new double[1000] 1000 int k=0; k 0 while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        } true {
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        } n = scan.nextInt() n scan.nextInt() scan.nextInt scan if(n==0)break; n==0 n 0 break; int[] a = new int[n]; a new int[n] n int sum=0; sum 0 for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                a[i]=scan.nextInt();
                sum+=a[i];
            } {
                a[i]=scan.nextInt();
                sum+=a[i];
            } a[i]=scan.nextInt() a[i] a i scan.nextInt() scan.nextInt scan sum+=a[i] sum a[i] a i double ave = (double)sum/n; ave (double)sum/n (double)sum n double var=0; var 0 for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            } {
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            } var =var+((a[i]-ave)*(a[i]-ave)/n) var var+((a[i]-ave)*(a[i]-ave)/n) var ((a[i]-ave)*(a[i]-ave)/n) (a[i]-ave)*(a[i]-ave) (a[i]-ave) a[i] a i ave (a[i]-ave) a[i] a i ave n ans[k] = Math.sqrt(var) ans[k] ans k Math.sqrt(var) Math.sqrt Math var k++ k for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        } int i=0; int i=0; i 0 i<k i k i++ i++ i {
            System.out.printf("%.5f\n",ans[i]);
        } {
            System.out.printf("%.5f\n",ans[i]);
        } System.out.printf("%.5f\n",ans[i]) System.out.printf System.out System System.out "%.5f\n" ans[i] ans i String[] args args public class Main {
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    }
} public class Main {
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    }
} Main
import java.util.Scanner;
import java.lang.Math;


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

        Scanner scan = new Scanner(System.in);
        int n;
        double[] ans = new double[1000];
        int k=0;
        while(true){
            n = scan.nextInt();
            if(n==0)break;
            int[] a = new int[n];
            int sum=0;
            for(int i=0;i<n;i++){
                a[i]=scan.nextInt();
                sum+=a[i];
            }
            double ave = (double)sum/n;
            double var=0;
            for(int i=0;i<n;i++){
                var =var+((a[i]-ave)*(a[i]-ave)/n);
            }
            ans[k] = Math.sqrt(var);
            k++;
        }
        for(int i=0;i<k;i++){
            System.out.printf("%.5f\n",ans[i]);
        }
    }
}
