import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	}
} Main public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	} main {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	} BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); in new BufferedReader(new InputStreamReader(System.in)) while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		} true {
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		} int sum=0 sum 0 n = Integer.parseInt(in.readLine()); n Integer.parseInt(in.readLine()) Integer.parseInt Integer in.readLine() in.readLine in if(n==0){
				break;
			} n==0 n 0 {
				break;
			} break; int[] s = new int[n]; s new int[n] n String[] nums = in.readLine().split(" "); nums in.readLine().split(" ") in.readLine().split in.readLine() in.readLine in " " for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			} {
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			} s[i] = Integer.parseInt(nums[i]) s[i] s i Integer.parseInt(nums[i]) Integer.parseInt Integer nums[i] nums i sum += s[i] sum s[i] s i double aveM = (double)sum/n; aveM (double)sum/n (double)sum n double process=0; process 0 for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			} int si s {
				process += (double)(Math.pow(si-aveM, 2));
			} {
				process += (double)(Math.pow(si-aveM, 2));
			} process += (double)(Math.pow(si-aveM, 2)) process (double)(Math.pow(si-aveM, 2)) Math.pow Math si-aveM si aveM 2 double dev = (double) Math.sqrt(process/n); dev (double) Math.sqrt(process/n) Math.sqrt Math process/n process n System.out.println(dev) System.out.println System.out System System.out dev String[] args args public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	}
} public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int sum=0, n = Integer.parseInt(in.readLine());
			if(n==0){
				break;
			}
			int[] s = new int[n];
			String[] nums = in.readLine().split(" ");
			for(int i=0; i<n; i++){
				s[i] = Integer.parseInt(nums[i]);
				sum += s[i];
			}
			double aveM = (double)sum/n;
			double process=0;
			for(int si : s){
				process += (double)(Math.pow(si-aveM, 2));
			}
			double dev = (double) Math.sqrt(process/n);
			System.out.println(dev);
		}
	}
}