import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	}
}
 import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int sum sum i; i double m m alpha; alpha while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		} true {
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		} sum=0 sum 0 alpha=0 alpha 0 int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0)break; n==0 n 0 break; int s[] = new int[n]; s new int[n] n for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			} i=0; 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 m = (double)sum/n m (double)sum/n (double)sum n for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			} i=0; i=0 i 0 i<n i n i++ i++ i {
				alpha+=Math.pow(s[i]-m,2);
			} {
				alpha+=Math.pow(s[i]-m,2);
			} alpha+=Math.pow(s[i]-m,2) alpha Math.pow(s[i]-m,2) Math.pow Math s[i]-m s[i] s i m 2 alpha/=n alpha n alpha=Math.sqrt(alpha) alpha Math.sqrt(alpha) Math.sqrt Math alpha System.out.println(alpha) System.out.println System.out System System.out alpha String[] args args public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	}
} public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	}
} Main
import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int sum,i;
		double m,alpha;
		while(true){
			sum=0;
			alpha=0;
			int n = sc.nextInt();
			if(n==0)break;
			int s[] = new int[n];
			for(i=0;i<n;i++){
				s[i]=sc.nextInt();
				sum+=s[i];
			}
			m = (double)sum/n;
			for(i=0;i<n;i++){
				alpha+=Math.pow(s[i]-m,2);
			}
			alpha/=n;
			alpha=Math.sqrt(alpha);
			System.out.println(alpha);
		}
	}
}

