import java.util.Scanner;

class Main {

	public static void main(String[] args) {

		int n;
		double a, m, b;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		}
		stdIn.close();
	}
} import java.util.Scanner; Scanner java.util class Main {

	public static void main(String[] args) {

		int n;
		double a, m, b;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		}
		stdIn.close();
	}
} Main public static void main(String[] args) {

		int n;
		double a, m, b;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		}
		stdIn.close();
	} main {

		int n;
		double a, m, b;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		}
		stdIn.close();
	} int n; n double a a m m b; b Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		} true {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		} b = 0.0 b 0.0 n = stdIn.nextInt() n stdIn.nextInt() stdIn.nextInt stdIn if(n == 0) {
				break;
			} n == 0 n 0 {
				break;
			} break; int[] s = new int[n]; s new int[n] n for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = stdIn.nextInt();
			} {
				s[i] = stdIn.nextInt();
			} s[i] = stdIn.nextInt() s[i] s i stdIn.nextInt() stdIn.nextInt stdIn double temp = 0.0; temp 0.0 for (Integer j : s) {
				temp += j;
			} Integer j s {
				temp += j;
			} {
				temp += j;
			} temp += j temp j m = (temp / n) m (temp / n) temp n int i = 0; i 0 for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			} Integer j s {
				b += Math.pow((j - m), 2);
				i++;
			} {
				b += Math.pow((j - m), 2);
				i++;
			} b += Math.pow((j - m), 2) b Math.pow((j - m), 2) Math.pow Math (j - m) j m 2 i++ i a = b / n a b / n b n System.out.format("%.8f\n", Math.sqrt(a)) System.out.format System.out System System.out "%.8f\n" Math.sqrt(a) Math.sqrt Math a stdIn.close() stdIn.close stdIn String[] args args
import java.util.Scanner;

class Main {

	public static void main(String[] args) {

		int n;
		double a, m, b;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			b = 0.0;
			n = stdIn.nextInt();
			if(n == 0) {
				break;
			}
			int[] s = new int[n];

			for (int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
			}

			double temp = 0.0;
			for (Integer j : s) {
				temp += j;
			}
			m = (temp / n);

			int i = 0;
			for (Integer j : s) {
				b += Math.pow((j - m), 2);
				i++;
			}
			a = b / n;
			System.out.format("%.8f\n", Math.sqrt(a));
		}
		stdIn.close();
	}
}