import java.util.*;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		}
	}
} import java.util.*; util.* java class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		}
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		}
	} main {
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		} true {
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		} int n = Integer.parseInt(sc.nextLine()); n Integer.parseInt(sc.nextLine()) Integer.parseInt Integer sc.nextLine() sc.nextLine sc double nDouble =(double)n; nDouble (double)n if(n==0){
				break;
			} n==0 n 0 {
				break;
			} break; String[] line= sc.nextLine().split(" "); line sc.nextLine().split(" ") sc.nextLine().split sc.nextLine() sc.nextLine sc " " double[] s = new double[n]; s new double[n] n double m=0; m 0 double sum=0; sum 0 double alpha=0; alpha 0 for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			} {
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			} s[i]=Double.parseDouble(line[i]) s[i] s i Double.parseDouble(line[i]) Double.parseDouble Double line[i] line i sum+=s[i] sum s[i] s i m=sum/nDouble m sum/nDouble sum nDouble sum=0 sum 0 for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sum+=(s[i]-m)*(s[i]-m);
			} {
				sum+=(s[i]-m)*(s[i]-m);
			} sum+=(s[i]-m)*(s[i]-m) sum (s[i]-m)*(s[i]-m) (s[i]-m) s[i] s i m (s[i]-m) s[i] s i m alpha=Math.sqrt(sum/n) alpha Math.sqrt(sum/n) Math.sqrt Math sum/n sum n System.out.printf("%.5f",alpha) System.out.printf System.out System System.out "%.5f" alpha System.out.println() System.out.println System.out System System.out String[] args args
import java.util.*;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		while(true){
			int n = Integer.parseInt(sc.nextLine());
			double nDouble =(double)n;
			if(n==0){
				break;
			}
			String[] line= sc.nextLine().split(" ");
			double[] s = new double[n];
			double m=0;
			double sum=0;
			double alpha=0;
			for(int i=0;i<n;i++){
				s[i]=Double.parseDouble(line[i]);
				sum+=s[i];
			}
			m=sum/nDouble;
			sum=0;
			for(int i=0;i<n;i++){
				sum+=(s[i]-m)*(s[i]-m);
			}
			alpha=Math.sqrt(sum/n);
			System.out.printf("%.5f",alpha);
			System.out.println();
		}
	}
}