import java.util.Scanner;


import java.lang.Math;
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    }
}
 import java.util.Scanner; Scanner java.util import java.lang.Math; Math java.lang public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        } true {
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0){
                break;
            } n==0 n 0 {
                break;
            } break; double s[] = new double[n]; s new double[n] n double m=0 m 0 a=0; a 0 for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                s[i] = sc.nextDouble();
                m+=s[i];
            } {
                s[i] = sc.nextDouble();
                m+=s[i];
            } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc m+=s[i] m s[i] s i m/=n m n for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                a+=(s[i]-m)*(s[i]-m);
            } {
                a+=(s[i]-m)*(s[i]-m);
            } a+=(s[i]-m)*(s[i]-m) a (s[i]-m)*(s[i]-m) (s[i]-m) s[i] s i m (s[i]-m) s[i] s i m a/=n a n System.out.printf("%.8f%n",Math.sqrt(a)) System.out.printf System.out System System.out "%.8f%n" Math.sqrt(a) Math.sqrt Math a sc.close() sc.close sc String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    }
} Main
import java.util.Scanner;


import java.lang.Math;
public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0){
                break;
            }
            double s[] = new double[n];
            double m=0,a=0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            for(int i=0;i<n;i++){
                a+=(s[i]-m)*(s[i]-m);
            }
            a/=n;
            System.out.printf("%.8f%n",Math.sqrt(a));
        }
        sc.close();
    }
}

