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));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	}
} 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));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	}
} Main public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	} main {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String[] tokuten; tokuten String line; line while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		} !(line = br.readLine()).equals("0") (line = br.readLine()).equals("0") (line = br.readLine()).equals (line = br.readLine()) line br.readLine() br.readLine br "0" {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		} int n = Integer.parseInt(line); n Integer.parseInt(line) Integer.parseInt Integer line tokuten = br.readLine().split(" ") tokuten br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double ave = 0; ave 0 for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				ave += Integer.parseInt(tokuten[i]);
			} {
				ave += Integer.parseInt(tokuten[i]);
			} ave += Integer.parseInt(tokuten[i]) ave Integer.parseInt(tokuten[i]) Integer.parseInt Integer tokuten[i] tokuten i ave = ave / n ave ave / n ave n double sd = 0; sd 0 for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			} {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			} sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n sd (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) Math.pow Math Integer.parseInt(tokuten[i]) - ave Integer.parseInt(tokuten[i]) Integer.parseInt Integer tokuten[i] tokuten i ave 2.0 n sd = Math.sqrt(sd) sd Math.sqrt(sd) Math.sqrt Math sd System.out.println(sd) System.out.println System.out System System.out sd String[] args args public class Main {

	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	}
} public class Main {

	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	}
} 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));
		String[] tokuten;
		String line;
		while (!(line = br.readLine()).equals("0")) {
			int n = Integer.parseInt(line);
			tokuten = br.readLine().split(" ");

			double ave = 0;
			for (int i = 0; i < n; i++) {
				ave += Integer.parseInt(tokuten[i]);
			}
			ave = ave / n;

			double sd = 0;
			for (int i = 0; i < n; i++) {
				sd += (Math.pow(Integer.parseInt(tokuten[i]) - ave, 2.0)) / n;
			}

			sd = Math.sqrt(sd);
			System.out.println(sd);
		}
	}
}