import java.util.*;
class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		}
	}
} import java.util.*; util.* java class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		}
	}
} Main public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		}
	} main {
		Scanner stdIn = new Scanner(System.in);
		while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		}
	} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		} true {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		} int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn if(n == 0) break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n int sum = 0; sum 0 for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = stdIn.nextInt();
				sum += s[i];
			} {
				s[i] = stdIn.nextInt();
				sum += s[i];
			} s[i] = stdIn.nextInt() s[i] s i stdIn.nextInt() stdIn.nextInt stdIn sum += s[i] sum s[i] s i double m = sum/(double)n; m sum/(double)n sum (double)n double a = 0.0; a 0.0 for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				a += (s[i] - m)*(s[i] - m);
			} {
				a += (s[i] - m)*(s[i] - m);
			} a += (s[i] - m)*(s[i] - m) a (s[i] - m)*(s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m a= a/(double)n a a/(double)n a (double)n System.out.println(Math.sqrt(a)) System.out.println System.out System System.out Math.sqrt(a) Math.sqrt Math a String[] args args
import java.util.*;
class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		while(true) {
			int n = stdIn.nextInt();
			if(n == 0) break;
			int[] s = new int[n];
			int sum = 0;
			for(int i = 0; i < n; i++) {
				s[i] = stdIn.nextInt();
				sum += s[i];
			}
			double m = sum/(double)n;
			double a = 0.0;
			for(int i = 0; i < n; i++) {
				a += (s[i] - m)*(s[i] - m);
			}
			a= a/(double)n;
			
			System.out.println(Math.sqrt(a));
			
		}
	}
}