import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	}
} Main public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	} main {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		} true {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0) break; n == 0 n 0 break; int[] scores = new int[n]; scores new int[n] n int sum = 0; sum 0 for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} scores[i] = sc.nextInt() scores[i] scores i sc.nextInt() sc.nextInt sc sum += scores[i] sum scores[i] scores i double ave = (double)sum/n; ave (double)sum/n (double)sum n double dev = 0; dev 0 for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			} {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			} double tmp = scores[i] - ave; tmp scores[i] - ave scores[i] scores i ave dev += tmp * tmp dev tmp * tmp tmp tmp dev = Math.pow(dev/n, 0.5) dev Math.pow(dev/n, 0.5) Math.pow Math dev/n dev n 0.5 System.out.println(dev) System.out.println System.out System System.out dev String[] args args public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	}
} public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while(true) {
			int n = sc.nextInt();

			if(n == 0) break;

			int[] scores = new int[n];

			int sum = 0;
			for (int i = 0; i < n; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = (double)sum/n;

			double dev = 0;
			for (int i = 0; i < n; i++) {
				double tmp = scores[i] - ave;
				dev += tmp * tmp;
			}
			dev = Math.pow(dev/n, 0.5);

			System.out.println(dev);
		}
	}
}