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 studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	}
} 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 studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	}
} Main public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while(true){

			int studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while(true){

			int studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while(true){

			int studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		} true {

			int studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		} int studentNum = Integer.parseInt(br.readLine()); studentNum Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if(studentNum == 0){
				break;
			} studentNum == 0 studentNum 0 {
				break;
			} break; String[] score = br.readLine().split(" "); score br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double scoreSum = 0; scoreSum 0 for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			} int i = 0; int i = 0; i 0 i < studentNum i studentNum i++ i++ i {

				scoreSum += Double.parseDouble(score[i]);
			} {

				scoreSum += Double.parseDouble(score[i]);
			} scoreSum += Double.parseDouble(score[i]) scoreSum Double.parseDouble(score[i]) Double.parseDouble Double score[i] score i double scoreAverage = scoreSum / studentNum; scoreAverage scoreSum / studentNum scoreSum studentNum double sigmaSum = 0; sigmaSum 0 for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			} int i = 0; int i = 0; i 0 i < studentNum i studentNum i++ i++ i {
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			} {
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			} double num = Double.parseDouble(score[i]) - scoreAverage; num Double.parseDouble(score[i]) - scoreAverage Double.parseDouble(score[i]) Double.parseDouble Double score[i] score i scoreAverage sigmaSum += num * num sigmaSum num * num num num double sigmaResult = sigmaSum / studentNum; sigmaResult sigmaSum / studentNum sigmaSum studentNum double alpha = Math.sqrt(sigmaResult); alpha Math.sqrt(sigmaResult) Math.sqrt Math sigmaResult System.out.printf("%.8f\n", alpha) System.out.printf System.out System System.out "%.8f\n" alpha br.close() br.close br 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 studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	}
} public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while(true){

			int studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	}
} 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 studentNum = Integer.parseInt(br.readLine());
			if(studentNum == 0){
				break;
			}

			String[] score = br.readLine().split(" ");

			double scoreSum = 0;

			for(int i = 0; i < studentNum;i++){

				scoreSum += Double.parseDouble(score[i]);
			}

			double scoreAverage = scoreSum / studentNum;

			double sigmaSum = 0;

			for (int i = 0;i < studentNum;i++){
				double num = Double.parseDouble(score[i]) - scoreAverage;
				sigmaSum += num * num;
			}

			double sigmaResult = sigmaSum / studentNum;

			double alpha = Math.sqrt(sigmaResult);

			System.out.printf("%.8f\n", alpha);
		}
		br.close();
	}
}