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