import java.util.Scanner;

public class Main {
	public static Scanner sc;
	public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	}

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

} Main public static Scanner sc; sc public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	} main {
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	} sc=new Scanner(System.in) sc new Scanner(System.in) while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		} true {
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		} Double n=sc.nextDouble() n sc.nextDouble() sc.nextDouble sc hou=(double) 0 hou (double) 0 sum=(double) 0; sum (double) 0 if(n==0)break; n==0 n 0 break; for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			} {
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			} Double s=sc.nextDouble(); s sc.nextDouble() sc.nextDouble sc hou+=s*s hou s*s s s sum+=s sum s Double kin=sum/n; kin sum/n sum n Double a=Math.sqrt((hou/n)-kin*kin); a Math.sqrt((hou/n)-kin*kin) Math.sqrt Math (hou/n)-kin*kin (hou/n) hou n kin*kin kin kin System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main {
	public static Scanner sc;
	public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	}

} public class Main {
	public static Scanner sc;
	public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	}

} Main
import java.util.Scanner;

public class Main {
	public static Scanner sc;
	public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	}

}