import java.util.Scanner;

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

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