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

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    }
} public class Main {
    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    }
} Main public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    } main {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    } java.util.Scanner sc = new java.util.Scanner(System.in); sc new java.util.Scanner(System.in) while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        } true {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) { break; } n == 0 n 0 { break; } break; int[] s = new int[n]; s new int[n] n double m = 0; m 0 for (int i = 0; i < n; i ++) {
                s[i] = sc.nextInt();
                m += s[i];
            } int i = 0; int i = 0; i 0 i < n i n i ++ i ++ i {
                s[i] = sc.nextInt();
                m += s[i];
            } {
                s[i] = sc.nextInt();
                m += s[i];
            } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc m += s[i] m s[i] s i m /= n m 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 a = Math.sqrt(a / n) a Math.sqrt(a / n) Math.sqrt Math a / n a n System.out.println(String.format("%10.8f", a)) System.out.println System.out System System.out String.format("%10.8f", a) String.format String "%10.8f" a String[] args args public class Main {
    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    }
} public class Main {
    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    }
} Main
public class Main {
    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

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

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", a));
        }
    }
}