import java.util.*;
public class Main {
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    }
} import java.util.*; util.* java public class Main {
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    }
} Main public static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    } main {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    } int i i j j k; k while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        } true {
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0)
                break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n double sum = 0; sum 0 for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            } i = 0; i = 0 i 0 i < n i n i++ i++ i {
                sum += s[i] = sc.nextInt();
            } {
                sum += s[i] = sc.nextInt();
            } sum += s[i] = sc.nextInt() sum s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc double m = sum/n; m sum/n sum n sum = 0 sum 0 for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            } i = 0; i = 0 i 0 i < n i n i++ i++ i {
                sum += Math.pow(s[i]-m,2);
            } {
                sum += Math.pow(s[i]-m,2);
            } sum += Math.pow(s[i]-m,2) sum Math.pow(s[i]-m,2) Math.pow Math s[i]-m s[i] s i m 2 System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5)) System.out.printf System.out System System.out "%.5f\n" Math.pow((double)sum/n,0.5) Math.pow Math (double)sum/n (double)sum n 0.5 String[] args args public class Main {
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    }
} public class Main {
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    }
} Main
import java.util.*;
public class Main {
    public static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
    	int i, j, k;
    	
    	while(true){
            int n = sc.nextInt();
            if(n == 0)
                break;
 
            int[] s = new int[n];
            double sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += s[i] = sc.nextInt();
            }
 
            double m = sum/n;
            sum = 0;
 
            for (i = 0; i < n; i++) {
                sum += Math.pow(s[i]-m,2);
            }
            System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
        }
    }
}
