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;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	}

}
 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;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			if (n == 0)
				break;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			if (n == 0)
				break;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			int n = sc.nextInt();
			if (n == 0)
				break;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		} true {
			int n = sc.nextInt();
			if (n == 0)
				break;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0)
				break;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			} n == 0 n 0 break; {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			} int[] s = new int[n]; s new int[n] n int sum1 = 0; sum1 0 double sum2 = 0; sum2 0 for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
					s[i] = sc.nextInt();
					sum1 += s[i];
				} {
					s[i] = sc.nextInt();
					sum1 += s[i];
				} s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc sum1 += s[i] sum1 s[i] s i double m = (double) sum1 / n; m (double) sum1 / n (double) sum1 n for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
					sum2 += (s[i] - m) * (s[i] - m);
				} {
					sum2 += (s[i] - m) * (s[i] - m);
				} sum2 += (s[i] - m) * (s[i] - m) sum2 (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m double sd = Math.sqrt((double) sum2 / n); sd Math.sqrt((double) sum2 / n) Math.sqrt Math (double) sum2 / n (double) sum2 n System.out.println(sd) System.out.println System.out System System.out sd sc.close() sc.close sc 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;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	}

} 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;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	}

} 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;
			else {
				int[] s = new int[n];
				int sum1 = 0;
				double sum2 = 0;
				for (int i = 0; i < n; i++) {
					s[i] = sc.nextInt();
					sum1 += s[i];
				}
				double m = (double) sum1 / n;
				for (int i = 0; i < n; i++) {
					sum2 += (s[i] - m) * (s[i] - m);
				}
				double sd = Math.sqrt((double) sum2 / n);
				System.out.println(sd);
			}
		}
		sc.close();
	}

}

