import java.util.*;
import java.lang.*;

/**
 * StandardDeviation
 */
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    }
} import java.util.*; util.* java import java.lang.*; lang.* java public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    } main {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        } true {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0)
                break; n == 0 n 0 break; int list[] = new int[n]; list new int[n] n double sum = 0; sum 0 for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                list[i] = sc.nextInt();
                sum += list[i];
            } {
                list[i] = sc.nextInt();
                sum += list[i];
            } list[i] = sc.nextInt() list[i] list i sc.nextInt() sc.nextInt sc sum += list[i] sum list[i] list i sum /= n sum n double ans = 0; ans 0 for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                ans += Math.pow((list[i] - sum), 2);
            } {
                ans += Math.pow((list[i] - sum), 2);
            } ans += Math.pow((list[i] - sum), 2) ans Math.pow((list[i] - sum), 2) Math.pow Math (list[i] - sum) list[i] list i sum 2 System.out.printf("%.8f\n", Math.sqrt((double) ans / n)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt((double) ans / n) Math.sqrt Math (double) ans / n (double) ans n String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    }
} Main
import java.util.*;
import java.lang.*;

/**
 * StandardDeviation
 */
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

            int list[] = new int[n];
            double sum = 0;
            for (int i = 0; i < n; i++) {
                list[i] = sc.nextInt();
                sum += list[i];
            }

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / n));
        }
    }
}
