import java.util.Scanner;

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

public class Main{
    public static void main(String args[]){
        try (Scanner sc = new Scanner (System.in)){
            while(true){
                int n = sc.nextInt();
                if(n==0){
                    break;
                }
                int [] scores = new int[n];
                double sum =0;
                for(int i=0;i<scores.length;i++){
                    scores[i]=sc.nextInt();
                    sum += scores[i];
                }
                double ave = sum/n;
                double varp=0;
                double var =0;
                for(int i=0;i<scores.length;i++){
                    varp += (scores[i]-ave)*(scores[i]-ave);
                }
                var = varp/n;
                System.out.printf("%f\n",Math.sqrt(var));
            }
        }
    }
}
