import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		}
} Main public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		} main {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		} Scanner scan=new Scanner(System.in); scan new Scanner(System.in) for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	} ; {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	} {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	} int a=scan.nextInt(); a scan.nextInt() scan.nextInt scan if(a==0) {
			break;
		} a==0 a 0 {
			break;
		} break; double ans=0; ans 0 int b[]=new int[a]; b new int[a] a double sum=0; sum 0 for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		} int i=0; int i=0; i 0 i<a i a i++ i++ i {
			b[i]=scan.nextInt();
			sum+=b[i];
		} {
			b[i]=scan.nextInt();
			sum+=b[i];
		} b[i]=scan.nextInt() b[i] b i scan.nextInt() scan.nextInt scan sum+=b[i] sum b[i] b i double hei=sum/a; hei sum/a sum a for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		} int i=0; int i=0; i 0 i<a i a i++ i++ i {
			ans+=Math.pow(b[i]-hei,2);
		} {
			ans+=Math.pow(b[i]-hei,2);
		} ans+=Math.pow(b[i]-hei,2) ans Math.pow(b[i]-hei,2) Math.pow Math b[i]-hei b[i] b i hei 2 ans=Math.sqrt(ans/a) ans Math.sqrt(ans/a) Math.sqrt Math ans/a ans a System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		}
} public class Main {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		}
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		for(;;) {
		int a=scan.nextInt();
		if(a==0) {
			break;
		}
		double ans=0;
		int b[]=new int[a];
		double sum=0;
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
			sum+=b[i];
		}
		double hei=sum/a;
		for(int i=0;i<a;i++) {
			ans+=Math.pow(b[i]-hei,2);
		}
		ans=Math.sqrt(ans/a);
		System.out.println(ans);
	}
		}
}
