import java.util.ArrayList;
import java.util.List;
import java.io.*;
import java.util.Scanner;
import java.math.*;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	}

} import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.io.*; io.* java import java.util.Scanner; Scanner java.util import java.math.*; math.* java public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	}

} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	} main {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		} true {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		} int n = Integer.parseInt(scan.nextLine()); n Integer.parseInt(scan.nextLine()) Integer.parseInt Integer scan.nextLine() scan.nextLine scan if (n == 0) {
				break;
			} n == 0 n 0 {
				break;
			} break; String sTmp = scan.nextLine(); sTmp scan.nextLine() scan.nextLine scan int sum = 0; sum 0 int[] s = new int[n]; s new int[n] n for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			} {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			} s[i] = Integer.parseInt(sTmp.split(" ")[i]) s[i] s i Integer.parseInt(sTmp.split(" ")[i]) Integer.parseInt Integer sTmp.split(" ")[i] sTmp.split(" ") sTmp.split sTmp " " i sum += s[i] sum s[i] s i double ave = (double)sum / (double)n; ave (double)sum / (double)n (double)sum (double)n double dv = 0; dv 0 for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			} {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			} dv += (ave - (double)s[i]) * (ave - (double)s[i]) dv (ave - (double)s[i]) * (ave - (double)s[i]) (ave - (double)s[i]) ave (double)s[i] s i (ave - (double)s[i]) ave (double)s[i] s i double res = Math.sqrt(dv / n); res Math.sqrt(dv / n) Math.sqrt Math dv / n dv n System.out.println(res) System.out.println System.out System System.out res String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	}

} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	}

} Main
import java.util.ArrayList;
import java.util.List;
import java.io.*;
import java.util.Scanner;
import java.math.*;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = Integer.parseInt(scan.nextLine());
			if (n == 0) {
				break;
			}
			String sTmp = scan.nextLine();
			int sum = 0;
			int[] s = new int[n];
 			for (int i = 0; i < n; i++) {
				s[i] = Integer.parseInt(sTmp.split(" ")[i]);
				sum += s[i];
			}
			double ave = (double)sum / (double)n;
			double dv = 0;
			for (int i = 0; i < n; i++) {
				dv += (ave - (double)s[i]) * (ave - (double)s[i]);
			}
			double res = Math.sqrt(dv / n);
			System.out.println(res);
		}
	}

}
