import java.io.IOException;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.Scanner;

class Main{
    private static final Scanner sc = new Scanner(System.in);
    private static final DecimalFormat fmt = new DecimalFormat("0.########");
    private static final PrintWriter out = new PrintWriter(System.out);
    public static void main(String[] Args) throws IOException{
        while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        }
        out.flush();
    }
} import java.io.IOException; IOException java.io import java.io.PrintWriter; PrintWriter java.io import java.text.DecimalFormat; DecimalFormat java.text import java.util.Scanner; Scanner java.util class Main{
    private static final Scanner sc = new Scanner(System.in);
    private static final DecimalFormat fmt = new DecimalFormat("0.########");
    private static final PrintWriter out = new PrintWriter(System.out);
    public static void main(String[] Args) throws IOException{
        while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        }
        out.flush();
    }
} Main private static final Scanner sc = new Scanner(System.in); sc new Scanner(System.in) private static final DecimalFormat fmt = new DecimalFormat("0.########"); fmt new DecimalFormat("0.########") private static final PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) public static void main(String[] Args) throws IOException{
        while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        }
        out.flush();
    } main {
        while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        }
        out.flush();
    } while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        } true {
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        } final int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc if(n==0) break; n==0 n 0 break; final int s[] = new int[n]; s new int[n] n for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            } int i = 0; int i = 0; i 0 i<s.length i s.length s s.length i++ i++ i {
                s[i] = Integer.parseInt(sc.next());
            } {
                s[i] = Integer.parseInt(sc.next());
            } s[i] = Integer.parseInt(sc.next()) s[i] s i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc double m = 0; m 0 for(final int e:s)
                m += e; final int e s m += e; m += e m e m /= n m n double a = 0; a 0 for(final int e:s)
                a += (e-m)* (e-m); final int e s a += (e-m)* (e-m); a += (e-m)* (e-m) a (e-m)* (e-m) (e-m) e m (e-m) e m out.println(fmt.format(Math.sqrt(a/n))) out.println out fmt.format(Math.sqrt(a/n)) fmt.format fmt Math.sqrt(a/n) Math.sqrt Math a/n a n out.flush() out.flush out String[] Args Args
import java.io.IOException;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.Scanner;

class Main{
    private static final Scanner sc = new Scanner(System.in);
    private static final DecimalFormat fmt = new DecimalFormat("0.########");
    private static final PrintWriter out = new PrintWriter(System.out);
    public static void main(String[] Args) throws IOException{
        while(true){
            final int n = Integer.parseInt(sc.next());
            if(n==0) break;
            final int s[] = new int[n];
            for(int i = 0; i<s.length; i++){
                s[i] = Integer.parseInt(sc.next());
            }
            double m = 0;
            for(final int e:s)
                m += e;
            m /= n;
            double a = 0;
            for(final int e:s)
                a += (e-m)* (e-m);

            out.println(fmt.format(Math.sqrt(a/n)));
        }
        out.flush();
    }
}