import java.util.Scanner;

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

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    }

} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args){

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    }

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

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    } main {

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        } true {
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        } int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if(n==0){ break; } n==0 n 0 { break; } break; double[] s = new double[n]; s new double[n] n int i = 0; i 0 double sum = 0; sum 0 double sumHensa = 0; sumHensa 0 double ans = 0; ans 0 for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            } i=0; i=0 i 0 i<n i n i++ i++ i {
                s[i] = scan.nextDouble();
                sum += s[i];
            } {
                s[i] = scan.nextDouble();
                sum += s[i];
            } s[i] = scan.nextDouble() s[i] s i scan.nextDouble() scan.nextDouble scan sum += s[i] sum s[i] s i double average = (double) sum / n; average (double) sum / n (double) sum n for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            } i=0; i=0 i 0 i<n i n i++ i++ i {
                sumHensa += (s[i] - average) * (s[i] - average);
            } {
                sumHensa += (s[i] - average) * (s[i] - average);
            } sumHensa += (s[i] - average) * (s[i] - average) sumHensa (s[i] - average) * (s[i] - average) (s[i] - average) s[i] s i average (s[i] - average) s[i] s i average ans = Math.sqrt( (double) sumHensa / n ) ans Math.sqrt( (double) sumHensa / n ) Math.sqrt Math (double) sumHensa / n (double) sumHensa n System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args){

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    }

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

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    }

} Main
import java.util.Scanner;

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

        Scanner scan = new Scanner(System.in); 
        while(true){
            int n = scan.nextInt();
            if(n==0){ break; }
            double[] s = new double[n];
            int i = 0;
            double sum = 0;
            double sumHensa = 0; 
            double ans = 0;

            for(i=0;i<n;i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            double average = (double) sum / n;

            for(i=0;i<n;i++){
                sumHensa += (s[i] - average) * (s[i] - average);
            }

            ans = Math.sqrt( (double) sumHensa / n );
            System.out.println(ans);
        }
        
    }

}
