import java.util.Scanner;
import java.util.*;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		while (n != 0) {
			double sum = 0;
			List<Integer> vals = new ArrayList<Integer>();
			for (int i = 0; i < n; i++) {
				int a = sc.nextInt();
				vals.add(a);
				sum += a;
			}
			double ave = sum/n;
			sum = 0;
			for (int i = 0; i < n; i++) {
				sum += (vals.get(i) - ave)*(vals.get(i) - ave);
			}
			double a = sum/n;
			a = Math.sqrt(a);
			System.out.println(String.format("%.5f", a));
			n = sc.nextInt();
		}
	}
}


/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