import java.util.Scanner;

public class Main{

	public static double beki2(double x){
		return x*x;
	}

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main{

	public static double beki2(double x){
		return x*x;
	}

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	}
} Main public static double beki2(double x){
		return x*x;
	} beki2 {
		return x*x;
	} return x*x; x*x x x double x x public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n int []s; s while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		} true {
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		} n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n==0)
				break; n==0 n 0 break; s = new int[n] s new int[n] n for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i]=sc.nextInt();
			} {
				s[i]=sc.nextInt();
			} s[i]=sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc double ave; ave int sum=0; sum 0 for(int i=0;i<n;i++){
				sum+=s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sum+=s[i];
			} {
				sum+=s[i];
			} sum+=s[i] sum s[i] s i ave = (double)sum/n ave (double)sum/n (double)sum n double vari=0; vari 0 for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				vari += beki2(s[i]-ave);
			} {
				vari += beki2(s[i]-ave);
			} vari += beki2(s[i]-ave) vari beki2(s[i]-ave) beki2 s[i]-ave s[i] s i ave vari/=n vari n double dev=Math.sqrt(vari); dev Math.sqrt(vari) Math.sqrt Math vari System.out.println(dev) System.out.println System.out System System.out dev String[] args args public class Main{

	public static double beki2(double x){
		return x*x;
	}

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	}
} public class Main{

	public static double beki2(double x){
		return x*x;
	}

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	}
} Main
import java.util.Scanner;

public class Main{

	public static double beki2(double x){
		return x*x;
	}

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n;
		int []s;
		while(true){
			n = sc.nextInt();
			if(n==0)
				break;
			s = new int[n];
			for(int i=0;i<n;i++){
				s[i]=sc.nextInt();
			}
			double ave;
			int sum=0;
			for(int i=0;i<n;i++){
				sum+=s[i];
			}
			ave = (double)sum/n;
			double vari=0;
			for(int i=0;i<n;i++){
				vari += beki2(s[i]-ave);
			}
			vari/=n;
			double dev=Math.sqrt(vari);
			System.out.println(dev);
		}
	}
}
