import java.util.Scanner;

public class Main{
    public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    }
} Main public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    } main {

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        } true {
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        } 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 int sum = 0; sum 0 for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            } int i =0; int i =0; i 0 i < n i n i++ i++ i {
                s[i] = sc.nextInt();
                sum = sum + s[i];
            } {
                s[i] = sc.nextInt();
                sum = sum + s[i];
            } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc sum = sum + s[i] sum sum + s[i] sum s[i] s i double ave = 0 ave 0 var = 0; var 0 ave = sum / (double)n ave sum / (double)n sum (double)n double sum2 = 0; sum2 0 for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            } int k = 0; int k = 0; k 0 k < n k n k++ k++ k {
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            } {
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            } sum2 = sum2 + (s[k] - ave) * (s[k] - ave) sum2 sum2 + (s[k] - ave) * (s[k] - ave) sum2 (s[k] - ave) * (s[k] - ave) (s[k] - ave) s[k] s k ave (s[k] - ave) s[k] s k ave var = sum2 / (double)n var sum2 / (double)n sum2 (double)n System.out.printf("%.8f\n",Math.sqrt(var)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(var) Math.sqrt Math var String[]arg arg public class Main{
    public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    }
} public class Main{
    public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    }
} Main
import java.util.Scanner;

public class Main{
    public static void main(String[]arg){

        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;
            int[] s = new int[n];

            int sum = 0;

            for(int i =0; i < n; i++){
                s[i] = sc.nextInt();
                sum = sum + s[i];
            }
            double ave = 0, var = 0;

            ave = sum / (double)n;

            double sum2 = 0;

            for(int k = 0; k < n; k++){
                sum2 = sum2 + (s[k] - ave) * (s[k] - ave);
            }

            var = sum2 / (double)n;

            System.out.printf("%.8f\n",Math.sqrt(var));

        }

    }
}
