import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        }
    }
} import java.util.*; util.* java class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        }
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        }
    } main {
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        } true {
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

            System.out.printf("%.8f\n",Math.sqrt(sum / n));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] test = new int[n]; test new int[n] n double[] tmp = new double[n]; tmp new double[n] n if(n == 0)  break; n == 0 n 0 break; double sum = 0; sum 0 for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                test[i] = sc.nextInt();
                sum += test[i];
            } {
                test[i] = sc.nextInt();
                sum += test[i];
            } test[i] = sc.nextInt() test[i] test i sc.nextInt() sc.nextInt sc sum += test[i] sum test[i] test i double avg = (double)sum / n; avg (double)sum / n (double)sum n sum = 0 sum 0 for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                sum += (test[i] - avg) * (test[i] - avg);
            } {
                sum += (test[i] - avg) * (test[i] - avg);
            } sum += (test[i] - avg) * (test[i] - avg) sum (test[i] - avg) * (test[i] - avg) (test[i] - avg) test[i] test i avg (test[i] - avg) test[i] test i avg System.out.printf("%.8f\n",Math.sqrt(sum / n)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(sum / n) Math.sqrt Math sum / n sum n String[] args args
import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            int[] test = new int[n];
            double[] tmp = new double[n];

            if(n == 0)  break;

            double sum = 0;
            for(int i = 0;i < n;i++){
                test[i] = sc.nextInt();
                sum += test[i];
            }
            double avg = (double)sum / n;
            
            sum = 0;
            for(int i = 0;i < n;i++){
                sum += (test[i] - avg) * (test[i] - avg);
            }

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