import java.util.Scanner;

import static java.lang.Math.pow;
import static java.lang.Math.sqrt;

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

        Scanner in = new Scanner(System.in);

        String input = in.nextLine();

        int cnt = Integer.parseInt(input);

        while(cnt != 0){
            double sum = 0.0;
            input = in.nextLine();
            String [] param_line = input.split(" ", 0);
            int [] points = new int[param_line.length];
            for(int i=0; i<points.length; i++){
                points[i] = Integer.parseInt(param_line[i]);
                sum += points[i];
            }

            double avg = sum/points.length;
            double tmp = 0;
            for(int i=0; i<points.length; i++)
                tmp += pow(points[i]-avg,2);

            double bunsan = tmp/points.length;
            double hyohen = sqrt(bunsan);

            System.out.printf("%.8f\n",hyohen);

            input = in.nextLine();
            cnt = Integer.parseInt(input);
        }
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz