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();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	}

} 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();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	} main {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		} true {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc double ave = 0.0; ave 0.0 double a = 0.0; a 0.0 double b; b if (n == 0)
				break; n == 0 n 0 break; int[] score = new int[n]; score new int[n] n for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			} {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			} score[i] = sc.nextInt() score[i] score i sc.nextInt() sc.nextInt sc ave = ave + score[i] ave ave + score[i] ave score[i] score i ave = ave / n ave ave / n ave n for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			} int j = 0; int j = 0; j 0 j < n j n j++ j++ j {
				a = a + (score[j] - ave) * (score[j] - ave);
			} {
				a = a + (score[j] - ave) * (score[j] - ave);
			} a = a + (score[j] - ave) * (score[j] - ave) a a + (score[j] - ave) * (score[j] - ave) a (score[j] - ave) * (score[j] - ave) (score[j] - ave) score[j] score j ave (score[j] - ave) score[j] score j ave a = a / n a a / n a n b = Math.sqrt(a) b Math.sqrt(a) Math.sqrt Math a System.out.println(b) System.out.println System.out System System.out b String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	}

} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	}

} 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();
			double ave = 0.0;
			double a = 0.0;
			double b;
			if (n == 0)
				break;
			int[] score = new int[n];
			for (int i = 0; i < n; i++) {
				score[i] = sc.nextInt();
				ave = ave + score[i];
			}
			ave = ave / n;
			for (int j = 0; j < n; j++) {
				a = a + (score[j] - ave) * (score[j] - ave);
			}
			a = a / n;
			b = Math.sqrt(a);
			System.out.println(b);
		}
	}

}
