import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	}
} Main public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	} main {
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	} Scanner scan=new Scanner(System.in); scan new Scanner(System.in) int n; n double ave ave d; d while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		} (n=scan.nextInt())!=0 (n=scan.nextInt()) n scan.nextInt() scan.nextInt scan 0 {
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		} int[] point=new int[n]; point new int[n] n ave=0 ave 0 for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				point[i]=scan.nextInt();
				ave+=point[i];
			} {
				point[i]=scan.nextInt();
				ave+=point[i];
			} point[i]=scan.nextInt() point[i] point i scan.nextInt() scan.nextInt scan ave+=point[i] ave point[i] point i ave/=(double)n ave (double)n d=0 d 0 for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				d+=(Math.pow((ave-point[i]),2));
			} {
				d+=(Math.pow((ave-point[i]),2));
			} d+=(Math.pow((ave-point[i]),2)) d (Math.pow((ave-point[i]),2)) Math.pow Math (ave-point[i]) ave point[i] point i 2 d/=(double)n d (double)n d=Math.sqrt(d) d Math.sqrt(d) Math.sqrt Math d System.out.printf("%.8f\n",d) System.out.printf System.out System System.out "%.8f\n" d scan.close() scan.close scan String[] args args public class Main {
	public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	}
} public class Main {
	public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	}
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner scan=new Scanner(System.in);
		int n;
		double ave,d;
		while((n=scan.nextInt())!=0){
			int[] point=new int[n];
			ave=0;
			for(int i=0;i<n;i++){
				point[i]=scan.nextInt();
				ave+=point[i];
			}
			ave/=(double)n;
			d=0;
			for(int i=0;i<n;i++){
				d+=(Math.pow((ave-point[i]),2));
			}
			d/=(double)n;
			d=Math.sqrt(d);
			System.out.printf("%.8f\n",d);
		}
		scan.close();
	}
}