import java.util.Scanner;

public 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	}

} import java.util.Scanner; Scanner java.util public 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	}

} 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	} main {
		Scanner scan = new Scanner(System.in);

		while (true) {
			int n = scan.nextInt();
			if (n == 0)
				break;
			int[] s = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while (true) {
			int n = scan.nextInt();
			if (n == 0)
				break;
			int[] s = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		} true {
			int n = scan.nextInt();
			if (n == 0)
				break;
			int[] s = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if (n == 0)
				break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n double m = 0; m 0 for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = scan.nextInt();
				m += s[i];
			} {
				s[i] = scan.nextInt();
				m += s[i];
			} s[i] = scan.nextInt() s[i] s i scan.nextInt() scan.nextInt scan m += s[i] m s[i] s i m /= n m n double a = 0; a 0 for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				a += Math.pow(s[i] - m, 2);
			} {
				a += Math.pow(s[i] - m, 2);
			} a += Math.pow(s[i] - m, 2) a Math.pow(s[i] - m, 2) Math.pow Math s[i] - m s[i] s i m 2 a = Math.sqrt(a / n) a Math.sqrt(a / n) Math.sqrt Math a / n a n System.out.println(a) System.out.println System.out System System.out a scan.close() scan.close scan System.exit(0) System.exit System 0 String[] args args public 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	}

} public 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	}

} Main
import java.util.Scanner;

public 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 = new int[n];
			double m = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m /= n;
			double a = 0;
			for (int i = 0; i < n; i++) {
				a += Math.pow(s[i] - m, 2);
			}
			a = Math.sqrt(a / n);

			System.out.println(a);

		}

		scan.close();
		System.exit(0);
	}

}