import java.util.*;
import java.lang.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		}
	}
} import java.util.*; util.* java import java.lang.*; lang.* java class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		}
	} main {
		Scanner sc = new Scanner(System.in);
		
		while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		} true {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		} int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc if (a == 0) break; a == 0 a 0 break; double sum = 0; sum 0 int[] scores = new int[a]; scores new int[a] a for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			} int i = 0; int i = 0; i 0 i < a i a i++ i++ i {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			} {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			} scores[i]=sc.nextInt() scores[i] scores i sc.nextInt() sc.nextInt sc sum+=scores[i] sum scores[i] scores i double m = sum/a; m sum/a sum a double variance = 0; variance 0 for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			} int i = 0; int i = 0; i 0 i < a i a i++ i++ i {
				variance += Math.pow(scores[i]-m, 2)/a;
			} {
				variance += Math.pow(scores[i]-m, 2)/a;
			} variance += Math.pow(scores[i]-m, 2)/a variance Math.pow(scores[i]-m, 2)/a Math.pow(scores[i]-m, 2) Math.pow Math scores[i]-m scores[i] scores i m 2 a System.out.println(Math.sqrt(variance)) System.out.println System.out System System.out Math.sqrt(variance) Math.sqrt Math variance String[] args args
import java.util.*;
import java.lang.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		while (true) {
			int a = sc.nextInt();
			if (a == 0) break;
			double sum = 0;
			int[] scores = new int[a];
			for (int i = 0; i < a; i++) {
				scores[i]=sc.nextInt();
				sum+=scores[i];
			}
			double m = sum/a;
			double variance = 0;
			for (int i = 0; i < a; i++) {
				variance += Math.pow(scores[i]-m, 2)/a;
			}
			System.out.println(Math.sqrt(variance));
		}
	}
}
