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];
                for(int i = 0;i < scores.length;i++){
                    scores[i] = sc.nextInt();
                }
                double average = 0,deviation = 0,variance = 0;
                int sum = 0;
                for(int i = 0;i < scores.length;i++){
                    sum = sum + scores[i];
                }
                average = (double)sum / scores.length;
                for(int i = 0;i < scores.length;i++){
                    deviation = deviation + (scores[i] - average)*(scores[i] - average);
                }
                variance = deviation / scores.length;
                System.out.println(Math.sqrt(variance));
            }
        }
    }
}

/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