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();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    }
} 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();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    }
} Main public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        while(true){
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    } main {
        Scanner sc=new Scanner(System.in);
        while(true){
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) while(true){
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        } true {
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        } int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int sum1=0; sum1 0 int sum2=0; sum2 0 if(n==0){
                break;
            } n==0 n 0 {
                break;
            } break; int[] scores; scores scores=new int[n] scores new int[n] n for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            } int i=0; int i=0; i 0 i<scores.length i scores.length scores scores.length i++ i++ i {
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            } {
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            } scores[i]=sc.nextInt() scores[i] scores i sc.nextInt() sc.nextInt sc sum1=sum1+scores[i] sum1 sum1+scores[i] sum1 scores[i] scores i sum2=sum2+scores[i]*scores[i] sum2 sum2+scores[i]*scores[i] sum2 scores[i]*scores[i] scores[i] scores i scores[i] scores i double ave=0; ave 0 ave=(double)sum1/n ave (double)sum1/n (double)sum1 n double var=0; var 0 var=(double)sum2/n-ave*ave var (double)sum2/n-ave*ave (double)sum2/n (double)sum2 n ave*ave ave ave System.out.println(Math.sqrt(var)) System.out.println System.out System System.out Math.sqrt(var) Math.sqrt Math var String[] args args public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        while(true){
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    }
} public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        while(true){
            int n=sc.nextInt();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    }
} 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();
            int sum1=0;
            int sum2=0;
            if(n==0){
                break;
            }
            int[] scores;
            scores=new int[n];
            for(int i=0;i<scores.length;i++){
                scores[i]=sc.nextInt();
                sum1=sum1+scores[i];
                sum2=sum2+scores[i]*scores[i];
            }
            double ave=0;
            ave=(double)sum1/n;
            double var=0;
            var=(double)sum2/n-ave*ave;
            System.out.println(Math.sqrt(var));
        }
    }
}
