import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	}
} import java.util.Arrays; Arrays java.util import java.util.HashMap; HashMap java.util import java.util.Map; Map java.util import java.util.Scanner; Scanner java.util public class Main {

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	} main {
		Scanner sc = new Scanner(System.in);

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			final int n = sc.nextInt();

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		} true {
			final int n = sc.nextInt();

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		} final int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0){
				break;
			} n == 0 n 0 {
				break;
			} break; int[] arr = new int[n]; arr new int[n] n long sum = 0; sum 0 for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				arr[i] = sc.nextInt();
				sum += arr[i];
			} {
				arr[i] = sc.nextInt();
				sum += arr[i];
			} arr[i] = sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc sum += arr[i] sum arr[i] arr i double sigma = 0; sigma 0 for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			} {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			} sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n)))) sigma (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n)))) (arr[i] - (sum / (double) (n))) arr[i] arr i (sum / (double) (n)) sum (double) (n) ((arr[i] - (sum / (double) (n)))) arr[i] arr i (sum / (double) (n)) sum (double) (n) sigma /= (double) (n) sigma (double) (n) System.out.printf("%.7f\n", Math.sqrt(sigma)) System.out.printf System.out System System.out "%.7f\n" Math.sqrt(sigma) Math.sqrt Math sigma String args[] args public class Main {

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	}
} public class Main {

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	}
} Main
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

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

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

			if(n == 0){
				break;
			}
			
			int[] arr = new int[n];
			long sum = 0;
			for (int i = 0; i < n; i++) {
				arr[i] = sc.nextInt();
				sum += arr[i];
			}

			double sigma = 0;
			for (int i = 0; i < n; i++) {
				sigma += (arr[i] - (sum / (double) (n))) * ((arr[i] - (sum / (double) (n))));
			}
			sigma /= (double) (n);

			System.out.printf("%.7f\n", Math.sqrt(sigma));
		}

	}
}