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 n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	}

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

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	}

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

		while(true){
			int n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while(true){
			int n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) while(true){
			int n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		} true {
			int n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		} int n; n if((n = Integer.parseInt(br.readLine())) == 0)
				break; (n = Integer.parseInt(br.readLine())) == 0 (n = Integer.parseInt(br.readLine())) n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br 0 break; String[] pointsStr = br.readLine().split(" "); pointsStr br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int[] points = new int[n]; points new int[n] n for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				points[i] = Integer.parseInt(pointsStr[i]);
			} {
				points[i] = Integer.parseInt(pointsStr[i]);
			} points[i] = Integer.parseInt(pointsStr[i]) points[i] points i Integer.parseInt(pointsStr[i]) Integer.parseInt Integer pointsStr[i] pointsStr i int sum = 0; sum 0 for(int point : points){
				sum += point;
			} int point points {
				sum += point;
			} {
				sum += point;
			} sum += point sum point double mean = (new Double(sum)) / n; mean (new Double(sum)) / n (new Double(sum)) n double disp = 0; disp 0 for(int point : points){
				disp += (point - mean) * (point - mean);
			} int point points {
				disp += (point - mean) * (point - mean);
			} {
				disp += (point - mean) * (point - mean);
			} disp += (point - mean) * (point - mean) disp (point - mean) * (point - mean) (point - mean) point mean (point - mean) point mean disp /= n disp n System.out.printf("%.8f%n", Math.sqrt(disp)) System.out.printf System.out System System.out "%.8f%n" Math.sqrt(disp) Math.sqrt Math disp 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 n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	}

} public class Main {

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

		while(true){
			int n;
			if((n = Integer.parseInt(br.readLine())) == 0)
				break;

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	}

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

			String[] pointsStr = br.readLine().split(" ");
			int[] points = new int[n];
			for(int i = 0;i < n;i++){
				points[i] = Integer.parseInt(pointsStr[i]);
			}

			int sum = 0;
			for(int point : points){
				sum += point;
			}
			double mean = (new Double(sum)) / n;
			double disp = 0;
			for(int point : points){
				disp += (point - mean) * (point - mean);
			}
			disp /= n;
			System.out.printf("%.8f%n", Math.sqrt(disp));
		}
	}

}