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

public class Main {
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	}
} 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 br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	}
} Main public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		} true {
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		} int num = Integer.parseInt(br.readLine()); num Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if(num == 0){
				break;
			} num == 0 num 0 {
				break;
			} break; int[] su = new int[num]; su new int[num] num String[] str = br.readLine().split(" "); str br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			} int i = 0; int i = 0; i 0 i < str.length i str.length str str.length i++ i++ i {
				su[i] = Integer.parseInt(str[i]);
			} {
				su[i] = Integer.parseInt(str[i]);
			} su[i] = Integer.parseInt(str[i]) su[i] su i Integer.parseInt(str[i]) Integer.parseInt Integer str[i] str i double sum = 0; sum 0 for(int i = 0; i < su.length; i++){
				sum += su[i];
			} int i = 0; int i = 0; i 0 i < su.length i su.length su su.length i++ i++ i {
				sum += su[i];
			} {
				sum += su[i];
			} sum += su[i] sum su[i] su i double avg = sum / num; avg sum / num sum num double result = 0; result 0 for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			} int i = 0; int i = 0; i 0 i < num i num i++ i++ i {
				result += (Math.pow((su[i] - avg), 2)/num);
			} {
				result += (Math.pow((su[i] - avg), 2)/num);
			} result += (Math.pow((su[i] - avg), 2)/num) result (Math.pow((su[i] - avg), 2)/num) Math.pow((su[i] - avg), 2) Math.pow Math (su[i] - avg) su[i] su i avg 2 num System.out.println(Math.sqrt(result)) System.out.println System.out System System.out Math.sqrt(result) Math.sqrt Math result String[] args args public class Main {
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	}
} public class Main {
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	}
} 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 br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int num = Integer.parseInt(br.readLine());
			if(num == 0){
				break;
			}
			int[] su = new int[num];
			String[] str = br.readLine().split(" ");

			for(int i = 0; i < str.length; i++){
				su[i] = Integer.parseInt(str[i]);
			}

			double sum = 0;

			for(int i = 0; i < su.length; i++){
				sum += su[i];
			}

			double avg = sum / num;
			double result = 0;

			for(int i = 0; i < num; i++){
				result += (Math.pow((su[i] - avg), 2)/num);
			}
			System.out.println(Math.sqrt(result));
		}
	}
}