import java.util.Scanner;
public class Main{
    public static void main(String[] args){
	Scanner scan = new Scanner(System.in);
	while(scan.hasNext()){
	    int n = Integer.parseInt(scan.nextLine());
	    if (n == 0) {
		break;
	    }
	    String[] input = scan.nextLine().split(" ");
	    int[] s = new int[n];
	    int count = 0;
	    for (int i = 0; i < n; i++) {
		s[i] = Integer.parseInt(input[i]);
		count += s[i];
	    }
	    double m = (double)count / n;
	    double sigma = 0;
	    for (int i = 0; i < n; i++) {
		sigma += (s[i] - m) * (s[i] - m);
	    }
	    double a = Math.sqrt(sigma / n);
	    System.out.println(a);
	}	
    }
}
/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