import java.util.Scanner;
import java.io.*;

class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		}
	}
} import java.util.Scanner; Scanner java.util import java.io.*; io.* java class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		}
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		}
	} main {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		} true {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if (n == 0) break; n == 0 n 0 break; int[] s; s s = new int[n] s new int[n] n int sum = 0; sum 0 for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i ++ i ++ i {
				s[i] = scan.nextInt();
				sum += s[i];
			} {
				s[i] = scan.nextInt();
				sum += s[i];
			} s[i] = scan.nextInt() s[i] s i scan.nextInt() scan.nextInt scan sum += s[i] sum s[i] s i double m = (double)sum / n; m (double)sum / n (double)sum n double shiguma = 0; shiguma 0 for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m); int i = 0; int i = 0; i 0 i < n i n i ++ i ++ i shiguma += (s[i] - m) * (s[i] - m); shiguma += (s[i] - m) * (s[i] - m) shiguma (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m double a = Math.sqrt(shiguma / n); a Math.sqrt(shiguma / n) Math.sqrt Math shiguma / n shiguma n System.out.printf("%f\n", a) System.out.printf System.out System System.out "%f\n" a String[] args args
import java.util.Scanner;
import java.io.*;

class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s;
			s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i ++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;
			double shiguma = 0;
			for (int i = 0; i < n; i ++) shiguma += (s[i] - m) * (s[i] - m);
			double a = Math.sqrt(shiguma / n);
			System.out.printf("%f\n", a);
		}
	}
}