import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    } main {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        } true {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        } int count = sc.nextInt(); count sc.nextInt() sc.nextInt sc if (count == 0) {
                break;
            } count == 0 count 0 {
                break;
            } break; double[] s = new double[count]; s new double[count] count double sum = 0; sum 0 for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            } int i = 0; int i = 0; i 0 i < count i count i++ i++ i {
                s[i] = sc.nextDouble();
                sum += s[i];
            } {
                s[i] = sc.nextDouble();
                sum += s[i];
            } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc sum += s[i] sum s[i] s i double average = sum / count; average sum / count sum count double res = 0; res 0 for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            } int i = 0; int i = 0; i 0 i < count i count i++ i++ i {
                res += Math.pow(s[i] - average, 2) / count;
            } {
                res += Math.pow(s[i] - average, 2) / count;
            } res += Math.pow(s[i] - average, 2) / count res Math.pow(s[i] - average, 2) / count Math.pow(s[i] - average, 2) Math.pow Math s[i] - average s[i] s i average 2 count System.out.println(Math.sqrt(res)) System.out.println System.out System System.out Math.sqrt(res) Math.sqrt Math res String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int count = sc.nextInt();
            if (count == 0) {
                break;
            }
            double[] s = new double[count];
            double sum = 0;
            for (int i = 0; i < count; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double average = sum / count;
            double res = 0;
            for (int i = 0; i < count; i++) {
                res += Math.pow(s[i] - average, 2) / count;
            }
            System.out.println(Math.sqrt(res));
        }
    }
}