import java.util.*;
public class Main{
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    }
 
} import java.util.*; util.* java public class Main{
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    }
 
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n double m m a2; a2 int s[] = new int[1000]; s new int[1000] 1000 while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        } true {
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        } n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n == 0)break; n == 0 n 0 break; m = 0 m 0 a2 = 0 a2 0 for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        		s[i] = sc.nextInt();
        		m += s[i];
        	} {
        		s[i] = sc.nextInt();
        		m += s[i];
        	} s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc m += s[i] m s[i] s i m = m/ n m m/ n m n for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	} {
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	} a2 += (s[i] - m)*(s[i] - m) / n a2 (s[i] - m)*(s[i] - m) / n (s[i] - m)*(s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m n System.out.printf("%.8f\n",Math.sqrt(a2)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(a2) Math.sqrt Math a2 String[] args args public class Main{
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    }
 
} public class Main{
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    }
 
} Main
import java.util.*;
public class Main{
 
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n;
        double m, a2;
        int s[] = new int[1000];
        while(true){
        	n = sc.nextInt();
        	if(n == 0)break;
        	m = 0;
        	a2 = 0; 
        	for(int i = 0; i < n; i++){
        		s[i] = sc.nextInt();
        		m += s[i];
        	}
        	m = m/ n;
        	for(int i = 0; i < n; i++){
        		a2 += (s[i] - m)*(s[i] - m) / n;
        	}
        	System.out.printf("%.8f\n",Math.sqrt(a2));
        }
    }
 
}