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

public class Main {

	public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	}

} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	}

} Main public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	} main {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	} Scanner scan = new java.util.Scanner(System.in); scan new java.util.Scanner(System.in) InputStreamReader input = new InputStreamReader(System.in); input new InputStreamReader(System.in) BufferedReader br = new BufferedReader(input); br new BufferedReader(input) StringBuilder sb = new StringBuilder(); sb new StringBuilder() while (true) {
			int n = Integer.parseInt(br.readLine());
			if (n==0) break;
			int[] s = new int[n];

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		} true {
			int n = Integer.parseInt(br.readLine());
			if (n==0) break;
			int[] s = new int[n];

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		} int n = Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if (n==0) break; n==0 n 0 break; int[] s = new int[n]; s new int[n] n String[] dataset = br.readLine().split(" "); dataset br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = Integer.parseInt(dataset[i]);
			} {
				s[i] = Integer.parseInt(dataset[i]);
			} s[i] = Integer.parseInt(dataset[i]) s[i] s i Integer.parseInt(dataset[i]) Integer.parseInt Integer dataset[i] dataset i int goukei = 0; goukei 0 for (int i : s) {
				goukei += i;
			} int i s {
				goukei += i;
			} {
				goukei += i;
			} goukei += i goukei i double m = (double)goukei / (double)n; m (double)goukei / (double)n (double)goukei (double)n double alfa2 = 0.0; alfa2 0.0 for (int i : s) {
				alfa2 += (i - m) * (i - m);
			} int i s {
				alfa2 += (i - m) * (i - m);
			} {
				alfa2 += (i - m) * (i - m);
			} alfa2 += (i - m) * (i - m) alfa2 (i - m) * (i - m) (i - m) i m (i - m) i m alfa2 = alfa2 / n alfa2 alfa2 / n alfa2 n double alfa = Math.sqrt(alfa2); alfa Math.sqrt(alfa2) Math.sqrt Math alfa2 System.out.println(alfa) System.out.println System.out System System.out alfa String[] args args public class Main {

	public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	}

} public class Main {

	public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	}

} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws IOException {
		// TODO ?????????????????????????????????????????????
		Scanner scan = new java.util.Scanner(System.in);

		InputStreamReader input = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(input);

		StringBuilder sb = new StringBuilder();

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

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

			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(dataset[i]);
			}
			int goukei = 0;

			for (int i : s) {
				goukei += i;
			}
			double m = (double)goukei / (double)n;

			double alfa2 = 0.0;

			for (int i : s) {
				alfa2 += (i - m) * (i - m);
			}

			alfa2 = alfa2 / n;

			double alfa = Math.sqrt(alfa2);
			System.out.println(alfa);
		}
	}

}