import java.util.Scanner;

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

		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, variance = 0, sum = 0;

			for (int i = 0; i < scores.length; i++) {
				sum += scores[i];

			}

			average = sum / n;

			sum = 0;

			for (int i = 0; i < scores.length; i++) {
				sum += (scores[i] - average) * (scores[i] - average);

			}

			variance = sum / n;

			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