import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	}

}
 import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	}

} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	} main {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int i i n; n double sum; sum double rec[]; rec double a; a while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		} true {
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		} n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n==0){
				break;
			} n==0 n 0 {
				break;
			} break; rec = new double[n] rec new double[n] n sum = 0.0 sum 0.0 a = 0.0 a 0.0 for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			} i=0; i=0 i 0 i<n i n i++ i++ i {
				rec[i] = sc.nextDouble();
				sum += rec[i];
			} {
				rec[i] = sc.nextDouble();
				sum += rec[i];
			} rec[i] = sc.nextDouble() rec[i] rec i sc.nextDouble() sc.nextDouble sc sum += rec[i] sum rec[i] rec i sum /= n sum n for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			} i=0; i=0 i 0 i<n i n i++ i++ i {
				a += Math.pow((rec[i]-sum), 2.0);
			} {
				a += Math.pow((rec[i]-sum), 2.0);
			} a += Math.pow((rec[i]-sum), 2.0) a Math.pow((rec[i]-sum), 2.0) Math.pow Math (rec[i]-sum) rec[i] rec i sum 2.0 a /= n a n a = Math.sqrt(a) a Math.sqrt(a) Math.sqrt Math a System.out.printf("%.8f\n",a) System.out.printf System.out System System.out "%.8f\n" a sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	}

} public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int i,n;
		double sum;
		double rec[];
		double a;

		while(true){
			n = sc.nextInt();
			if(n==0){
				break;
			}
			rec = new double[n];
			sum = 0.0;
			a = 0.0;

			for(i=0;i<n;i++){
				rec[i] = sc.nextDouble();
				sum += rec[i];
			}
			sum /= n;
			for(i=0;i<n;i++){
				a += Math.pow((rec[i]-sum), 2.0);
			}
			a /= n;
			a = Math.sqrt(a);

			System.out.printf("%.8f\n",a);
		}

		sc.close();


	}

}

