import 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	}
} import java.util.*; util.* java 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	}
} 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	} main {
		Scanner sc=new Scanner(System.in);
		while(true){
			int n=sc.nextInt();
			if(n==0){
				break;
			}else{
				int sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) while(true){
			int n=sc.nextInt();
			if(n==0){
				break;
			}else{
				int sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		} true {
			int n=sc.nextInt();
			if(n==0){
				break;
			}else{
				int sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		} int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0){
				break;
			}else{
				int sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			} n==0 n 0 {
				break;
			} break; {
				int sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			} int sum=0; sum 0 int[] s=new int[n]; s new int[n] n for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				} int i=0; int i=0; i 0 i<n i n i++ i++ i {
					s[i]=sc.nextInt();
					sum+=s[i];
				} {
					s[i]=sc.nextInt();
					sum+=s[i];
				} s[i]=sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc sum+=s[i] sum s[i] s i double m=(double)sum/(double)n; m (double)sum/(double)n (double)sum (double)n double a=0; a 0 for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				} int i=0; int i=0; i 0 i<n i n i++ i++ i {
					a+=(s[i]-m)*(s[i]-m);
				} {
					a+=(s[i]-m)*(s[i]-m);
				} a+=(s[i]-m)*(s[i]-m) a (s[i]-m)*(s[i]-m) (s[i]-m) s[i] s i m (s[i]-m) s[i] s i m a=a/n a a/n a n System.out.printf("%.8f\n",Math.sqrt(a)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(a) Math.sqrt Math a 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	}
} 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	}
} Main
import 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 sum=0;
				int[] s=new int[n];
				for(int i=0;i<n;i++){
					s[i]=sc.nextInt();
					sum+=s[i];
				}
				double m=(double)sum/(double)n;
				double a=0;
				for(int i=0;i<n;i++){
					a+=(s[i]-m)*(s[i]-m);
				}
				a=a/n;
				System.out.printf("%.8f\n",Math.sqrt(a));
			}
		}
	}
}