import java.io.IOException;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	}

} import java.io.IOException; IOException java.io import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	}

} Main public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	} main {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc double s = 0; s 0 double d = 0; d 0 while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			} a != 0 a 0 {
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			} int c[] = new int[a]; c new int[a] a for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				} int b=0; int b=0; b 0 b<a b a ++b ++b b {
					c[b]=sc.nextInt();
					s += c[b];
				} {
					c[b]=sc.nextInt();
					s += c[b];
				} c[b]=sc.nextInt() c[b] c b sc.nextInt() sc.nextInt sc s += c[b] s c[b] c b s = s/a s s/a s a for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				} int b=0; int b=0; b 0 b<a b a ++b ++b b {
					d += Math.pow(s-c[b], 2);
				} {
					d += Math.pow(s-c[b], 2);
				} d += Math.pow(s-c[b], 2) d Math.pow(s-c[b], 2) Math.pow Math s-c[b] s c[b] c b 2 d=Math.sqrt(d/a) d Math.sqrt(d/a) Math.sqrt Math d/a d a System.out.println(d) System.out.println System.out System System.out d d=0 d 0 s=0 s 0 a = sc.nextInt() a sc.nextInt() sc.nextInt sc String[] args args public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	}

} public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	}

} Main
import java.io.IOException;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.nextInt();
			}
	}

}