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

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

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

    } main {
        Scanner scan = new java.util.Scanner(System.in);
        for(;;){
            int n = scan.nextInt();
            double sum = 0;
            double m = 0;
            if(n == 0)break;
            double[] s = new double[n];
            for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }
            m = (double)sum / n;
            double a = 0;
            for(int i = 0; i < n; i++){
                a += (s[i] - m) * (s[i] - m);
            }
            double ans = Math.sqrt(a / n);
            if(ans >= 0){
                System.out.println(ans);
            }
        }

    } Scanner scan = new java.util.Scanner(System.in); scan new java.util.Scanner(System.in) for(;;){
            int n = scan.nextInt();
            double sum = 0;
            double m = 0;
            if(n == 0)break;
            double[] s = new double[n];
            for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }
            m = (double)sum / n;
            double a = 0;
            for(int i = 0; i < n; i++){
                a += (s[i] - m) * (s[i] - m);
            }
            double ans = Math.sqrt(a / n);
            if(ans >= 0){
                System.out.println(ans);
            }
        } ; {
            int n = scan.nextInt();
            double sum = 0;
            double m = 0;
            if(n == 0)break;
            double[] s = new double[n];
            for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }
            m = (double)sum / n;
            double a = 0;
            for(int i = 0; i < n; i++){
                a += (s[i] - m) * (s[i] - m);
            }
            double ans = Math.sqrt(a / n);
            if(ans >= 0){
                System.out.println(ans);
            }
        } {
            int n = scan.nextInt();
            double sum = 0;
            double m = 0;
            if(n == 0)break;
            double[] s = new double[n];
            for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }
            m = (double)sum / n;
            double a = 0;
            for(int i = 0; i < n; i++){
                a += (s[i] - m) * (s[i] - m);
            }
            double ans = Math.sqrt(a / n);
            if(ans >= 0){
                System.out.println(ans);
            }
        } int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan double sum = 0; sum 0 double m = 0; m 0 if(n == 0)break; n == 0 n 0 break; double[] s = new double[n]; s new double[n] n for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            } int i = 0; int 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 m = (double)sum / n m (double)sum / n (double)sum n double a = 0; a 0 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 double ans = Math.sqrt(a / n); ans Math.sqrt(a / n) Math.sqrt Math a / n a n if(ans >= 0){
                System.out.println(ans);
            } ans >= 0 ans 0 {
                System.out.println(ans);
            } 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 java.util.Scanner(System.in);
        for(;;){
            int n = scan.nextInt();
            double sum = 0;
            double m = 0;
            if(n == 0)break;
            double[] s = new double[n];
            for(int i = 0; i < n; i++){
                s[i] = scan.nextDouble();
                sum += s[i];
            }
            m = (double)sum / n;
            double a = 0;
            for(int i = 0; i < n; i++){
                a += (s[i] - m) * (s[i] - m);
            }
            double ans = Math.sqrt(a / n);
            if(ans >= 0){
                System.out.println(ans);
            }
        }

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

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

    }
}